ALDOL AND MICHAEL ADDITIONS OF FLUORINATED NITROALKANES TO ALDEHYDES, KETONES, AND ALPHA,BETA-UNSATURATED CARBONYL-COMPOUNDS

2,2,2-Trifluoronitroethane (1) and 3,3,3-trifluoro-2-nitropropane (2), despite their great propensity to undergo HF elimination with base, can be added to aldehydes with KF or neutral alumina (nitroaldol products 7-15). With basic alumina (neat components) they even add to alpha,beta-unsaturated aldehydes, ketones, esters, and nitriles (gamma-nitro carbonyl derivatives and nitrile 27-35). Doubly lithiated difluoro and trifluoro nitro derivatives (H, L) can be generated from the corresponding nitroethanes and -propanes (1-3) with butyllithium (THF, -100 to -70-degrees-C) and added to aldehydes and ketones to give nitroaldols (nitroethanols 11, 12, 16-21) and ''homonitroaldols'' (nitropropanols 36-38). In essentially all cases, mixtures of diastereoisomers are formed. Through O-silyltrifluoronitroaldols (22-26) it is possible to enrich one of the diastereoisomers by 3:1 (Scheme 4). Some transformations of the nitro compounds obtained lead to CF3-substituted aminoethanols (39-46, by catalytic hydrogenation on Raney nickel), a nitrobutanol (30 --> 48, with Et3SiH), and a ketone (30 --> 49, with Bu3SnH).