Aldol‐ und Michael‐Additionen fluorierter Nitroalkane an Aldehyde, Ketone und α,β‐ungesättigte Carbonylverbindungen1,2)

Aldol and Michael Additions of Fluorinated Nitroalkanes to Aldehydes, Ketones, and α,β‐Unsaturated Carbonyl Compounds1,2) 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 α,β‐unsaturated aldehydes, ketones, esters, and nitriles (γ‐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°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).