Highly enantioselective synthesis of long chain alkyl trifluoromethyl carbinols and β-thiotrifluoromethyl carbinols through lipases
摘要:
Among a variety of lipases tested, Candida antarctica lipase has been found to promote the enantioselective acylation of long chain alkyl trifluoromethyl carbinols 1a-4a and beta-thiotrifluoromethyl carbinols 5a-7a, producing both R and S enantiomeric alcohols in good to excellent chemical yield and enantioselectivity. In all cases the lipase preferentially acylates the S enantiomer, irrespective the presence or not of a sulfur atom in beta position to the hydroxyl group, When the reaction was carried out on the non-fluorinated substrates 1c-2c, the process occurred much faster and with higher e.e. of the less reacting enantiomer than when conducted on the fluorinated substrates. Copyright (C) 1996 Elsevier Science Ltd
A new, practical and efficient sulfone-mediated synthesis of trifluoromethyl ketones from alkyl and alkenyl bromides
摘要:
We report herein a new and efficient method to prepare trifluoromethyl ketones from the corresponding bromides through sulfones in good yields. (c) 2005 Elsevier Ltd. All rights reserved.
long-chain triflouromethyl ketones achieved by metallation of the corresponding iodides in the presence of an equimolar amount of tert-butyllithium, followed by reaction with a fluoroacylating agent. Metallation occurs quantitatively at −78°C and, in contrast to what has been generally recommended, there is no need to add the second equivalent of base, since its presence may be detrimental if other electrophilic
α-Trifluoromethyl amines (IV) were prepared in three steps: preparation of α-trifluoromethyl ketones (I), their conversion tobenzyloximes (II), and reduction of the oximes (II) with lithium aluminium hydride and sodium methoxide. For example, α-trifluoromethyltridecylamine was obtained from the reduction of trifluoromethyl dodecyl ketone benzyl oxime.
Despite the very low acidity of the inert α C−H bonds (pKa≈42.6), directasymmetric α-C(sp3)−H addition of N-unprotected propargylic amines to trifluoromethyl ketones has been achieved by using a chiral pyridoxal as the carbonyl catalyst, producing a broad variety of chiral alkynyl β-aminoalcohols in high yields with excellent stereoselectivities (up to 84 % yield, >20 : 1 dr, 99 % ee).
尽管惰性 α C−H 键的酸度非常低 (p K a ≈ 42.6),但通过使用手性吡哆醛,已经实现了 N-未保护的炔丙胺与三氟甲基酮的直接不对称 α-C( sp 3 )−H 加成作为羰基催化剂,以高产率和出色的立体选择性(高达 84% 产率,>20:1 dr,99% ee)生产多种手性炔基 β-氨基醇。
Access to Trifluoromethylketones from Alkyl Bromides and Trifluoroacetic Anhydride by Photocatalysis
作者:Hai‐Wu Du、Yi‐Dan Du、Xian‐Wang Zeng、Wei Shu
DOI:10.1002/anie.202308732
日期:2023.9.18
Catalytic methods for direct access to aliphatic trifluoromethyl ketones from feedstocks remain underdeveloped, partially owing to the high reactivity and instability of the trifluoroacetyl radical. Reported herein is the photocatalytic synthesis of trifluoromethyl ketones fromalkylbromides and trifluoroacetic anhydride. The reaction features visible-light catalysis and halogen-atom transfer (XAT)