Catalytic asymmetric cyanosilylation of ketones, aldehydes, thioketones, thioaldehydes, imines and hydrazones
One aspect of the present invention relates to a method for the catalytic asymmetric cyanosilylation of ketones, aldehydes, thioketones, thioaldehydes, imines and hydrazones. The critical elements of the method are: a non-racemic chiral tertiary-amine-containing catalyst; a substrate selected from the group consisting of ketones, aldehydes, thioketones, thioaldehydes, imines and hydrazones; and a silyl cyanide, e.g., trimethylsilyl cyanide. In preferred embodiments, the substrate is a ketone or aldehyde. A preferred embodiment of the present invention relates to practicing the method in a halocarbon solvent, e.g., chloroform. Another preferred embodiment of the present invention relates to practicing the method in an ester solvent, e.g., ethyl acetate. In certain embodiments, the methods of the present invention produce a silyl cyanohydrin with an enantiomeric excess greater than about 80%. In certain embodiments, the methods of the present invention produce a silyl cyanohydrin with an enantiomeric excess greater than about 90%.
1. A method of cyanosilylation of a substrate, comprising the step of combining a silyl cyanide, a substrate selected from the group consisting of ketones, aldehydes, thioketones, thioaldehydes, imines and hydrazones, and a chiral non-racemic catalyst, wherein said chiral non-racemic catalyst is a tertiary amine, phosphine or arsine, and wherein said chiral non-racemic catalyst catalyzes the addition of said silyl cyanide to said substrate to give a chiral non-racemic silyl cyanohydrin.
2. The method of claim 1 , wherein said substrate is a ketone or aldehyde.
3. The method of claim 1 , wherein said silyl cyanide is a trialkylsilyl cyanide.
4. The method of claim 1 , wherein said silyl cyanide is trimethylsilyl cyanide.
5. The method of claim 1 , wherein said chiral non-racemic catalyst is a tertiary amine.
6. The method of claim 1 , wherein said chiral non-racemic catalyst is a cinchona alkaloid.
7. The method of claim 1 , wherein said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR, (DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
8. The method of claim 1 , wherein said substrate is a ketone or aldehyde; and said silyl cyanide is a trialkylsilyl cyanide.
9. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is a trialkylsilyl cyanide; and said chiral non-racemic catalyst is a tertiary amine, phosphine or arsine.
10. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is a trialkylsilyl cyanide; and said chiral non-racemic catalyst is a tertiary amine.
11. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is a trialkylsilyl cyanide; and said chiral non-racemic catalyst is a cinchona alkaloid.
12. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is a trialkylsilyl cyanide; and said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR, (DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
13. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is trimethylsilyl cyanide; and said chiral non-racemic catalyst is a tertiary amine, phosphine or arsine.
14. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is trimethylsilyl cyanide; and said chiral non-racemic catalyst is a tertiary amine.
15. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is trimethylsilyl cyanide; and said chiral non-racemic catalyst is a cinchona alkaloid.
16. The method of claim 1 , wherein said substrate is a ketone or aldehyde; said silyl cyanide is trimethylsilyl cyanide; and said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR, (DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
17. The method of claim 1 , wherein the enantiomeric excess or diastereomeric excess of the chiral non-racemic silyl cyanohydrin is greater than about 50%.
18. The method of claim 1 , wherein the enantiomeric excess or diastereomeric excess of the chiral non-racemic silyl cyanohydrin is greater than about 70%.
19. The method of claim 1 , wherein the enantiomeric excess or diastereomeric excess of the chiral non-racemic silyl cyanohydrin is greater than about 90%.
20. A method of asymmetric cyanosilylation represented by Scheme 1:
wherein
X represents O, S, NR′, or NN(R′)(R″);
R represents independently for each occurrence alkyl, cycloalkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R′ represents independently for each occurrence alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R″ represents independently for each occurrence H, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R′ and R″ are not identical;
the product is chiral and non-racemic; and
chiral non-racemic catalyst is a chiral non-racemic tertiary amine, phosphine, or arsine.
21. The method of claim 20 , wherein X represents O.
22. The method of claim 20 , wherein R represents independently for each occurrence alkyl.
23. The method of claim 20 , wherein R represents independently for each occurrence methyl.
24. The method of claim 20 , wherein said chiral non-racemic catalyst is a chiral non-racemic tertiary amine.
25. The method of claim 20 , wherein said chiral non-racemic catalyst is a cinchona alkaloid.
26. The method of claim 20 , wherein said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR,(DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
27. The method claim 20 , wherein X represents O; and R represents independently for each occurrence alkyl.
28. The method of claim 20 , wherein X represents O; R represents independently for each occurrence alkyl; and said chiral non-racemic catalyst is a chiral non-racemic tertiary amine.
29. The method of claim 20 , wherein X represents O; R represents independently for each occurrence alkyl; and said chiral non-racemic catalyst is a cinchona alkaloid.
30. The method of claim 20 , wherein X represents O; R represents independently for each occurrence alkyl; and said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR, (DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
31. The method of claim 20 , wherein X represents O; and R represents independently for each occurrence methyl.
32. The method of claim 20 , wherein X represents O; R represents independently for each occurrence methyl; and said chiral non-racemic catalyst is a chiral non-racemic tertiary amine.
33. The method of claim 20 , wherein X represents O; R represents independently for each occurrence methyl; and said chiral non-racemic catalyst is a cinchona alkaloid.
34. The method of claim 20 , wherein X represents O; R represents independently for each occurrence methyl; and said chiral non-racemic catalyst is quinidine, (DHQ) 2 PHAL, (DHQD) 2 PHAL, (DHQ) 2 PYR, (DHQD) 2 PYR, (DHQ) 2 AQN, (DHQD) 2 AQN, DHQ-CLB, DHQD-CLB, DHQ-MEQ, DHQD-MEQ, DHQ-AQN, DHQD-AQN, DHQ-PHN, or DHQD-PHN.
35. The method of claim 20 , wherein the enantiomeric excess or diastereomeric excess of the product is greater than about 50%.
36. The method of claim 20 , wherein the enantiomeric excess or diastereomeric excess of the product is greater than about 70%.
37. The method of claim 20 , wherein the enantiomeric excess or diastereomeric excess of the product is greater than about 90%.