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Org. Synth. 2012, 89, 243-254
DOI: 10.15227/orgsyn.089.0243
Synthesis of (2R)-3-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]-2-methylpropanal by Rhodium-Catalyzed Asymmetric Hydroformylation
Submitted by Gene W. Wong, Tyler T. Adint, and Clark R. Landis1.
Checked by Neil Strotman, James Cuff, and David Hughes. .
1. Procedure
Caution! Carbon monoxide is a highly toxic gas and manipulations should be conducted in a well-ventilated fume hood in the vicinity of a carbon monoxide detector. Hydrogen gas is highly flammable and explosive gas. Precautions should be taken when using synthesis gas (H2/CO mixtures).
A. Allyl (t-butyldimethyl)silyl ether 1. An oven-dried three-necked, 500-mL round-bottomed flask equipped with a 3-cm PTFE-coated oval stir bar is charged with allyl alcohol (8.6 g, 0.15 mol, 1.0 equiv), imidazole (21.1 g, 0.31 mol, 2.1 equiv), and dimethylformamide (100 mL). (Note 1) The flask is fitted with a gas inlet adapter connected to a nitrogen line and a gas bubbler. The other two necks are capped with rubber septa; a thermocouple probe is inserted through one of the septa. (Note 2) The stirred solution is cooled to 4 °C with an ice-water bath, then t-butyldimethylsilyl chloride (25.5 g, 0.17 mol, 1.1 equiv) is added in portions over 2 min. (Note 3) The water bath is removed and the hazy solution is stirred 15 h at 22-23 °C. (Note 4) The reaction mixture is transferred to a 500-mL separatory funnel along with hexanes (200 mL) and water (60 mL). After mixing and settling, the aq. layer is removed and the organic layer washed with brine (75 mL). The hazy organic layer is filtered through a bed of sodium sulfate (50 g) in a medium porosity sintered glass funnel into a 500-mL round-bottomed flask, using hexanes (2 x 50 mL) to rinse the filter cake. The filtrate is concentrated by rotary evaporation (40 °C, 20 mmHg) to an oil (22 g). Since a substantial portion of the product co-distills during concentration, the distillate from the receiver flask is re-concentrated, providing additional product (2.8 g). The combined crude product is purified by column chromatography (Note 5) to afford allyl (t-butyldimethyl)silyl ether 1 (18.1-18.5 g, 71-73% yield) as a colorless oil. (Note 6)
B. (2R)-3-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-2-methylpropanal 2.In a glovebox, bis[(S,S,S)-DiazaPhos-SPE] (9.2 mg, 0.0070 mmol, 0.024 mol%) is added to a 20 mL vial followed by 0.22 mL CDCl3. To a separate 4 mL vial is added Rh(acac)(CO)2 (10 mg) followed by 1.94 mL toluene to prepare a 20 mM stock solution; 0.29 mL (1.5 mg, 0.0058 mmol, 0.020 mol%) of this stock solution is transferred to the 20 mL vial containing the ligand solution (Notes (Note 7), (Note 8)). Allyl (t-butyldimethyl)silyl ether 1 (5.00 g, 6.17 mL, 29 mmol, 1.0 equiv) is added to the vial. The solution is divided into 4 x 4 mL vials, each containing a 5-mm glass bead, and loaded into a Symyx Heated Orbital Shaker System (HOSS) contained within the glove box. (Note 9) The system is taken through 3 cycles of pressurization (150 psig of 1:1 H2:CO)/depressurization (0 psig) to replace the nitrogen atmosphere with synthesis gas. The system is pressurized with 150 psig 1:1 H2:CO and heated to 60 °C for 16 h. (Note 10) The mixture is cooled and the system depressurized, then the vials are removed from the glove box. (Note 15) The hydroformylation reaction mixture is purified immediately (Note 16) by flash column chromatography (Note 17) to afford colorless oils of branched isomer (R)-2 (3.24-3.43 g, 55-58% yield, Notes (Note 18)(Note 19)(Note 20)) and linear isomer 3 (1.62-1.70 g, 27-29% yield, (Note 21)).
2. Notes
1. The following reagents and solvents in step A were used as received: allyl alcohol (Sigma-Aldrich), imidazole (Acros, 99%), t-butyldimethylsilyl chloride (Acros, 98%), anhydrous DMF (Sigma-Aldrich, 99.8%), hexanes (Fisher, ACS reagent, >98.5%), ethyl acetate (Fisher, ACS reagent, >99.5%) and silica gel (Fisher, 230-400 mesh, 60 Å).
2. The internal temperature is monitored using a J-Kem Gemini digital thermometer with a Teflon-coated T-Type thermocouple probe (12-inch length, 1/8 inch outer diameter, temperature range -200 to +250 °C).
3. The reaction warmed to 25 °C over 5 min after addition of TBS-Cl.
4. The reaction was monitored by TLC, 5% EtOAc/hexanes, Rf 0.6, KMnO4 stain.
5. Silica gel (250 g) was slurry-packed in a 5-cm diameter column using 2.5% EtOAc/hexanes. The product was eluted with 2.5% EtOAc/hexanes, collecting 100 mL fractions. Fractions 5-13 were combined and concentrated by rotary evaporation (40 °C, 20 mmHg) to afford 1 (4.5-15.4 g) as a colorless oil. The distillate from concentration was re-concentrated to provide an additional 2.7-4.0 g (combined yield, 18.1-18.5 g, 71-73%). The distillate from the final product concentration was assayed by 1H NMR using toluene as an internal standard, indicating 2.4 g (10% yield) 1 was present in the distillate.
6. Allyl (t-butyldimethyl)silyl ether 1 has the following physical and spectroscopic data: 1H NMR pdf(400 MHz, CDCl3)δ: 0.09 (s, 6 H), 0.93 (s, 9 H), 4.18-4.20 (m, 2 H), 5.07-5.11 (m, 1 H), 5.25-5.30 (m, 1 H), 5.89-5.97 (m, 1 H); 13C NMR pdf(100 MHz, CDCl3)δ: -5.0, 18.6, 26.2, 64.3, 114.1, 137.8; GC-MS (EI) m/z: 172 (6 %) [M+], 157 (6%), [M - CH3], 116 (31%), 115 (100%) [M - t-Bu], 99 (21%), 85 (69%) [M - Me2,t-Bu], 75 (28%), 59 (48%); GC purity: 98% (tR = 4.4 min; conditions: Agilent DB35MS column; 30 m x 0.25 mm; initial temp 60 °C, ramp at 20 °C/min to 280 °C, hold 15 min).
7. The following reagents and solvents in step B were used as received by the checkers: dicarbonylacetylacetonato rhodium(I) (Strem), toluene (Sigma Aldrich, anhydrous, >99.9%), CDCl3 (Sigma-Aldrich, 99.8% atom % D), SynGas (49% carbon monoxide/51% hydrogen, Airgas) and bis[(S,S,S)-DiazaPhos-SPE] ligand: 2,2',2",2'''-(1,2-phenylenebis[(1S,3S)-tetrahydro-5,8-dioxo-1H-[1,2,4]diazaphospholo[1,2-a]pyridazine-2,1,3(3H)-triyl])tetrakis(N-[(1S)-1-phenylethyl])benzamide (Sigma-Aldrich). The ligand was prepared by the submitters according to their published procedure.2 The submitters recrystallized dicarbonylacetylacetonato rhodium(I) from toluene and hexanes as fine green crystals. CHCl3 may be used instead of CDCl3.
8. Accurate volumes were measured and transferred using an Eppendoft(r) pipette.
9. Symyx HOSS equipment is described on the Symyx website. http://symyx.desantisbreindel.com/page.php?ID=71
10. The submitter's equipment and experimental protocol are outlined in this Note and in Notes (Note 11)(Note 12)(Note 13)(Note 14). A heavy wall reaction tube (Ace Glass #15 Ace-Tread(r), 30 cm length x 38.1 mm O.D., 185 mL capacity) and a 0.5 x 0.125 inch magnetic stir bar are dried in a 125 °C oven overnight. In a glove box, the reaction tube is charged with stock solutions of Rh(acac)(CO)2 and Bis[(S,S,S)-DiazaPhos-SPE] using a 1000 μL Eppendoft(r) pipette followed by 5 grams of substrate. The reaction tube is attached to the reactor head (Note 11). Notably, the addition of the alkene to the catalyst solution resulted in a yellow-white suspension due to partial precipitation of ligand and/or catalyst-ligand complex. A blast shield must be used whenever the reactor is pressurized and safety procedures for using pressure tubes described in the Ace-Glass(r) catalog should be reviewed and followed. The assembled reactor is removed from the glove box, placed in a fume hood, connected to the synthesis gas source and taken through 5 cycles of pressurization (150 psig of 1:1 H2:CO)/depressurization (0 psig) to replace the nitrogen atmosphere with synthesis gas (Notes (Note 12), (Note 13), Figure 2). The reactor is then submerged in a heated silicon oil bath at the desired temperature. As synthesis gas is consumed, the reactor is repressurized to 150 psi to maintain approximately constant pressure (Note 14). After 2-3 hours (~30-40 psi of synthesis gas consumed) the suspension transforms to a homogeneous yellow solution. In six hours, ~90 psi of synthesis gas is consumed. At the end of the reaction time, the reactor is depressurized.
11. A custom-made reactor head used for hydroformylations is shown in Figure 1. The following parts were used to assemble the reactor head: a, Alltech® septum (High-temp, 3/8 in., AT79231) for aliquot-abstractions using a gas-tight syringe, b, Swagelok® Brass 1-Piece 40 Series Ball Valve (1.6 Cv, 1/4 in. MNPT x 1/4 in. Swagelok Tube Fitting; product #: B-43M4-247S4), c, Swagelok® Brass Pipe Fitting, Cross (1/4 in. Female NPT; product #:B-4-CS), d, Brass Pipe Fitting, Street Tee, (1/4 in. Female NPT x 1/4 in. Male NPT x 1/4 in. Female NPT; product #:B-4-ST), e, Brass pressure release valve, 150 psi-350 psi (1/4 in. Female NPT; product #:B-4CPA-VI-150), f, Ashcroft® 0-160 psig pressure gauge (1/4 in. NPT, 3.5 in. Dial; McMaster-Carr 3846K311 0-160 psig range), g, Brass Pipe Fitting, Close Nipple (1/4 in. Male NPT), h, #15 Ace-Thred® (15 mm thread, 1/4 in. NPT PTFE Swagelok adapter; Prod. #: 5844-74), i, Kalrez® 6375 O-ring (9.30mm x 2.40 mm Part #: K31016K6375), j, #15 Ace Glass® pressure tube (30.5 cm L, 38.1 mm OD, Prod. #: 8648-33), k, Swagelok® Brass 1-Piece 40 Series 3-Way Ball Valve (0.75 Cv, 1/4 in. FNPT; product #: B-43XF4), l, Brass Pipe Fitting (1/4 in. male NPT to 1/4 in. male Swagelok Tube Fitting), m, SS tubing (1/4 in OD, 2 1/2 in. length), and n, Swagelok® SS Instrumentation Quick-Connect Stem w/ Valve, (0.2 Cv, 1/4 in. Swagelok Tube Fitting, Part #: SS-QC4-D-400). Threads b, d, f, g, and l were wrapped with PTFE tape prior to assembly. A thorough pressure check of reactor should be taken before conducting an experiment. The most common source of a leak is between the brass pipe fitting g and the plastic #15 Ace-Thread adapter h. Pressure release valve e is calibrated by pressurizing to 150 psig and loosening check valve until triggering, followed by tightening a quarter turn. Once assembled with the 185-mL pressure tube, the reactor is rather cumbersome to transport-the use of an 11.5" (W) x 13.5" (L) x 5.25"(D) Rubbermaid® dishpan with a 3"(D) x 1" (W) rectangle cut in the tub on the width side was used to hold the reactor.
12. A reverse-threaded regulator is connected to a synthesis gas cylinder and Swagelok(r) Quick-Connects are used to attach to the reactor manifold. The synthesis gas cylinder was obtained from AirGas Inc. as a custom mixture (48.3±2% carbon monoxide balanced with hydrogen gas).
13. The reactor has two possible points of entry: Swagelok(r) Ball valve b fitted with a GC septum, for gas-tight syringe aliquots, and the Swagelok(r) 3-way Ball Valve k, for pressurizing and depressurizing the reactor. In Figure 2, k is opened carefully to the synthesis gas cylinder, charging the apparatus to 150 psig (it is advisable to set the regulator on the cylinder to ca. 150 psig and to have a safety shield in place). The valve on k is then opened to vent, releasing synthesis gas from the apparatus. After the pressure is reduced to <40 psi, the valve is turned back to the original closed position constituting one cycle. This procedure is repeated for five cycles and the reactor pressure is set at 150 psi. The glass tube of the reactor is lowered into the oil bath for hydroformylation as seen in the far-right picture.
14. Synthesis gas is added manually to maintain at least 100 psig reactor pressure. It is not advisable to maintain reactor pressure by keeping the reactor open to the regulator on the synthesis gas cylinder because, in the event of a leak on the reactor or supply lines, large amounts of H2 and CO could be released. A carbon monoxide detector is installed near the gas cylinder. Commonly, the synthesis gas line is detached from the reactor at the Swagelok(r) Quick-Connect during reaction and reconnected when adding more gas. However, if the synthesis gas line is not needed for other reactions, the Swagelok(r) Quick-Connect system can remain assembled throughout the reaction.
15. 1H NMR of the crude product mixture indicated >99% conversion of alkene and a branched: linear (2:3) ratio of 2:1.
16. Aldehyde 2 is air-sensitive and flash chromatography should be performed immediately after depressurizing the reactor and the purified product stored in a freezer.
17. Silica gel (250 g) was slurry-packed in a 5-cm diameter column using 5% EtOAc/hexanes. The product was eluted with 5% EtOAc/hexanes, collecting 50 mL fractions, monitored by TLC. (10% EtOAc/hexanes, Rf 1 = 0.7, (R)-2 = 0.38, 3 = 0.31, visualized with potassium permanganate stain, prepared as follows: 3 g KMnO4, 20 g potassium carbonate, 5 mL of a 5% (w/w) solution of aqueous sodium hydroxide, and 300 mL of deionized water.) Fractions 9-26 were combined and concentrated by rotary evaporation (40 °C, 20 mmHg) to afford 2 (3.24-3.43 g) as a colorless oil. Fractions 29-38 were combined and concentrated by rotary evaporation (40 °C, 20 mmHg) to afford 3 (1.62-1.70 g) as a colorless oil.
18. (2R)-3-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]-2-methylpropanal 2 has the following physical and spectroscopic data: [α]D25 -34 (c 1.0, CH2Cl2); 1H NMR pdf(500 MHz, CDCl3)δ: 0.06 (s, -Si(CH3)2C(CH3)3, 6 H), 0.89 (s, -Si(CH3)2C(CH3)3, 9 H), 1.10 (d, J = 6.9 Hz, -CHCH3, 3 H), 2.52-2.56 (m, -CHCH3, 1 H), 3.82 (dd, J = 6.4, 10.2 Hz, -CH2OSi, 1 H), 3.86 (dd, J = 5.2 Hz, 10.2, -CH2OSi, 1 H), 9.74 (d, J = 1.6 Hz, CHO-CH, 1 H); 13C NMR pdf(125 MHz, CDCl3)δ: -5.33, -5.31, 10.5, 18.4, 26.0, 49.0, 63.7, 204.9; IR (neat): 2957, 2931, 2859, 1736 (C=O), 1473, 1258, 1101, 1033, 838, 778 cm-1; GC-MS m/z (relative intensity): 145 (100) [M - t-Bu], 115 (95) [SiMe2t-Bu], 101 (31), 85 (25) [Sit-Bu], 75 (54), 59 (25); GC purity: 98% (tR = 7.4 min, same conditions as in note 6); ee 94-96% determined by SFC analysis of benzylamine reductive amination derivative as described in (Note 20). The aldehyde oxidizes at a rate of about 1% per week when stored in a -20 oC freezer.
19. The (S)-enantiomer of 2 was prepared by the same procedure using Bis[(R,R,S)-DiazaPhos-SPE] as ligand; [α]D25 +33 (c 1.0, CH2Cl2); ee 88%.
20. The submitters determined chiral purity by gas chromatographic analysis on a Varian Chrompack system using a β-DEX 225 capillary column from Supelco, 30 m x 0.25 mm ID x 0.25 um film thickness. The analytical method used to resolve the enantiomers as follow: 65 °C hold for 70 min, tR(R)-2: 60.8 min, tR(S)-2: 62.4 min. The checkers determined chiral purity by formation of the reductive amination product with benzylamine and analysis by supercritical fluid chromatography (SFC): tandem columns: 25 cm OZ : 25cm OZ, isocratic 8% 25mM i-butylamine in 2-propanol, 100 bar, 2.0 mL/min for 18 min. tR (R)-4 = 11.5 min, tR (S)-4 = 14 min. Procedure for the preparation of the reductive amination product with benzylamine follows.
To a 20-mL vial equipped a 0.7 cm stir bar is added sequentially sodium triacetoxyborohydride (235 mg, 1.1 mmol), chloroform (2 mL), aldehyde 2 (73 mg, 0.36 mmol), and benzylamine (37 mg, 0.34 mmol). The heterogeneous mixture is stirred 16 h at ambient temperature, then quenched with 5 mL sat. NaHCO3, stirring the biphasic mixture for 5 min. Dichloromethane (10 mL) is added, the layers are separated, and the organic layer dried by filtering through 2 g of sodium sulfate. The filtrate is concentrated by rotary evaporation (40 °C, 20 mmHg) to afford crude 4 (115 mg). The product is purified by silica gel chromatography using 10 g silica with an eluent of 97:2:0.5 CH2Cl2:MeOH:Et3N, collecting 10 mL fractions. Fractions 7-10 were combined and concentrated by rotary evaporation to provide product 4 (68 mg, 67% yield) as a colorless oil having the following physical and spectroscopic data: TLC: Rf = 0.1 (97:2:0.5 CH2Cl2:MeOH:Et3N); 1H NMR pdf(500 MHz, CDCl3)δ: 0.04 (s, 6 H), 0.89 (s, 9 H), 0.91 (d, J = 6.7 Hz, 3 H), 1.68 (br s, 1 H), 1.85-1.91 (m, 1 H), 2.51 (dd, J = 6.0, 11.6 Hz, 1 H), 2.68 (dd, J = 6.8, 11.6 Hz, 1 H), 3.50-3.57 (m, 2 H), 3.77-3.82 (m, 2 H), 7.25-7.26 (m, 1 H), 7.31-7.33 (m, 4 H); 13C NMR pdf(125 MHz, CDCl3)δ: -5.24, -5.21, 15.6, 18.5, 26.1, 36.1, 53.6, 54.5, 127.0, 128.3, 128.5, 140.9.
21. Linear product 3 has the following spectroscopic data: 1H NMR pdf(400 MHz, CDCl3)δ: 0.04 (s, -Si(CH3)2C(CH3)3, 6 H), 0.88 (s, -Si(CH3)2C(CH3)3, 9 H), 1.86 (tt, J = 6.0, 7.1 Hz -CH2CH2CH2-, 2 H), 2.50 (dt, J = 7.1, 1.8 Hz, CH2CHO, 2 H), 3.65 (t, J = 6.0 Hz, -CH2OSi, 3 H), 9.79 (t, J = 1.7 Hz, CHO, 1 H); 13C NMR pdf(100 MHz, CDCl3)δ: -5.2, 18.5, 25.7, 26.1, 41.0, 62.3, 202.9; GC purity: 96% (tR = 7.9 min, same conditions as in (Note 6))
Handling and Disposal of Hazardous Chemicals
The procedures in this article are intended for use only by persons with prior training in experimental organic chemistry. All hazardous materials should be handled using the standard procedures for work with chemicals described in references such as "Prudent Practices in the Laboratory" (The National Academies Press, Washington, D.C., 2011 www.nap.edu). All chemical waste should be disposed of in accordance with local regulations. For general guidelines for the management of chemical waste, see Chapter 8 of Prudent Practices.
These procedures must be conducted at one's own risk. Organic Syntheses, Inc., its Editors, and its Board of Directors do not warrant or guarantee the safety of individuals using these procedures and hereby disclaim any liability for any injuries or damages claimed to have resulted from or related in any way to the procedures herein.
3. Discussion
Protected "Roche Aldehydes" (e.g., 2, (2R)-3-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-2-methylpropanal) are common starting materials for the synthesis of polyketides and related molecules.3,4 Compared with the common reduction-to-alcohol-followed-by-selective-oxidation-to-aldehyde route to 2 from "Roche Ester",4 hydroformylation of the protected commodity monomer, allyl alcohol, provides Roche Aldehyde derivatives rapidly, at low cost, and in an easily scalable process. For comparison purposes we have collected the following approximate costs of substrates, normalized to 25 g units, from a common supplier: Roche ester ($350/25g), allyl alcohol ($1.00/25g). The only byproducts of the enantioselective hydroformylation of 1 is the corresponding linear aldehyde; although achiral the linear aldehyde is isolated cleanly and constitutes a useful synthetic material also. On larger scales, it should be possible to separate the linear and branched aldehydes by careful vacuum distillation; we have not yet optimized the distillation conditions. An advantage of hydroformylation routes to chiral aldehydes is the absence of acids or bases in the reaction solution that catalyze racemization and condensation reactions. We note that although the Roche Ester has been synthesized by asymmetric hydrogenation of the methyl 2-(hydroxymethyl)-prop-2-enoate,5 there is no report of a catalytic hydrogenation route to enantiopure Roche Aldehyde.
Figure 1. The submitters assembled reactor with parts indicated
Figure 1. The submitters assembled reactor with parts indicated
Synthesis of (2R)-3-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]-2-methylpropanal by Rhodium-Catalyzed Asymmetric Hydroformylation
References and Notes
  1. Department of Chemistry, University of Wisconsin, Madison, Wisconsin, 53706-1322. Email: Landis@chem.wisc.edu. We thank The Dow Chemical Company for their donation of Rh(acac)(CO)2. Funding was provided by the National Science Foundation (CHE-0715491 and a graduate fellowship for G.W.W.).
  2. Clark, T. P.; Landis, C. R.; Freed, S. L.; Klosin, K.; Abboud, K. A. J. Am. Chem. Soc. 2005, 127, 5040-5042.
  3. For a general review on polyketides stereotetrads, see: Koskinen, A. M. P.; Karisalmi, K. Chem. Soc. Rev. 2005, 34, 677-690.
  4. Roche Aldehyde for use in natural product syntheses see: (a) Früstner, A.; Nevado, C.; Waser, M.; Tremblay, M.; Chevrier, C.; Teply, F.; Aïssa, C.; Moulin, E.; Müller, O. J. Am. Chem. Soc.2007, 129, 9150-9161; (b) Canova, S.; Bellosta, V.; Bigot, A.; Mailliet, P.; Mignani, S.; Cossy, J. Org. Lett. 2007, 9, 145-148; (c) Ferrié, L.; Reymond, S.; Capdevielle, P.; Cossy, J. Org. Lett. 2006, 8, 3441-3443; (d) Ehrlich, G.; Kalesse, M. Synlett 2005, 4, 655-657; (e) Smith, A. B., III, Brandt, B. M. Org. Lett. 2001, 3, 1685-1688.
  5. (a) Qiu, M.; Wang, D.-Y.; Hu, X.-P.; Huang, J.-D.; Yu, S.-B.; Deng, J.; Duan, Z.-C.; Zheng, Z. Tetrahedron: Asymmetry 2009, 20, 210-213. (b) Pautigny, C.; Jeulin, S.; Ayad, T.; Zhang, Z.; Genêt, J.-P.; Ratovelomanana-Vidal, V. Adv. Synth. Catal. 2008, 350, 2525-2532. (c) Holz, J.; Schäffner, B.; Zayas, O.; Spannenberg, A.; Börner A. Adv. Synth. Catal. 2008, 350, 2533-2545. (d) Wassenaar, J.; Kuil, M.; Reek J. N. H. Adv. Synth. Catal. 2008, 350, 1610-1614. (e) Jeulin, S.; Ayad, T.; Ratovelomanana-Vidal, V.; Genêt, J.-P. Adv. Synth. Catal. 2007, 349, 1592-1596. (f) Shimizu, H.; Saito, T.; Kumobayashi, H. Adv. Synth. Catal. 2003, 345, 185-189.

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

Silane, (1,1-dimethylethyl)dimethyl(2-propen-1-yloxy)-; (85807-85-8)

Silane, chloro(1,1-dimethylethyl)dimethyl-; (18162-48-6)

Prop-2-en-1-ol; (107-18-6)

Rhodium, dicarbonyl(2,4-pentanedionato-κ-O2,κ-O4)-, (SP-4-2)-; (14874-82-9)

Benzamide, 2,2',2'',2'''-[1,2-phenylenebis[(1S,3S)-tetrahydro-5,8-dioxo-1H-[1,2,4]diazaphospholo[1,2-a]pyridazine-2,1,3(3H)-triyl]]tetrakis[N-[(1S)-1-phenylethyl]-; (851770-14-4)

Propanal, 3-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-2-methyl-, (2R)-; (97826-89-6),

Butanal, 4-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-; (8718 4-81-4)

Clark R. Landis was born in Aurora, IL in 1956. After completing his Ph.D. at the University of Chicago in 1983 under the direction of Jack Halpern, Professor Landis held professional positions at the Monsanto Company Corporate Research Lab, the University of Colorado-Boulder, and, since 1990, the University of Wisconsin-Madison. His research interests include bonding theory, computational methods, instrumentation development, chiral ligand synthesis, enantioselective catalysis, catalytic alkene polymerization, and the mechanisms of catalytic reactions.
Gene W. Wong was born in Reno, Nevada in 1985. He received his undergraduate chemistry degree from University of Nevada-Reno, where he conducted research with Prof. Brian J. Frost. He then moved to University of Wisconsin-Madison, where he is currently pursuing a Ph.D. in the research group of Prof. Clark R. Landis as a NSF Predoctoral Fellow. His research focuses on the development of bisdiazaphospholane libraries and rhodium catalyzed hydroformylation.
Tyler T. Adint was born in Fairbanks, Alaska in 1984. He received his undergraduate degree in 2003 from Lewis & Clark College, where he conducted research with Prof. Louis Y. Kuo. He is now pursuing his Ph.D. at the University of Wisconsin-Madison in the research group of Prof. Clark R. Landis. His current research interests concern the synthesis of bisdiazaphospholane ligands that utilize secondary interactions to control selectivity in rhodium catalyzed hydroformylations.
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