Synthesis of Fluorinated β-Ketosulfones and gem-Disulfones by Nucleophilic Fluoroalkylation of Esters and Sulfinates with Di- and Monofluoromethyl Sulfones
摘要:
An efficient and practically useful method for the preparation of alpha-functionalized mono- and difluoro(phenylsulfonyl)methanes by using a nucleophilic fluoroalkylation methodology was developed. alpha,alpha-Difluoro-P-ketosulfones, alpha-monofluoro-beta-ketosulfones, and alpha-fluoro disulfones were successfully prepared in excellent yields by nucleophilic fluoroalkylation of esters and sulfinates with PhSO2CF2H and PhSO2CH2F reagents.
Mixed Organofluorine−Organosilicon Chemistry. 13. One-Pot Synthesis of Difluoroaldols from Acylsilanes and Trifluoromethyltrimethylsilane. Application to the Synthesis of a Difluoro Analogue of Egomaketone
3 were synthesized in a one-pot procedure involving an acylsilane 1, trifluoromethyltrimethylsilane (TFMTMS), and an aldehyde. The key intermediate of this reaction is a difluoroenoxysilane 2. Ytterbium triflate proved to be a very efficient catalyst for promoting the aldol type reaction under very mild conditions. The potential of this reaction for the convergent synthesis of difluorinated compounds
Acetyltrimethylsilane, Trifluoromethyltrimethylsilane, and Prenyl Esters: A Three-Component System for the Synthesis of <i>g</i><i>em</i>-Difluoroanalogues of Monoterpenes
Optimized conditions leading to either the desired enol silyl ether or the unprecedented methyl(trifluoromethyl)trimethylsilyl carbinol 4 have been achieved. The prenylation of the enol silyl ether gives a 9/1 mixture of regioisomers, in favor of the expected ketone 1. Treatment of 1 with vinylmagnesium bromide leads to (+/-)-4,4-difluorolinalool 7. Reaction with the lithium enolate of ethyl diethylphosphonoacetate
Trifluorotrimethylsilane reacts with acylsilanes to give the corresponding difluoroenoxysilanes via the Brook rearrangement of the alcoholate adducts. The difluoroenoxysilane reacts in situ with various types of electrophilic substrates, leading to gem-difluoro functionalized derivatives in a one-pot methodology. This paper describes reactions with Michael accepters, prenyl, benzyl and glycosyl donors leading to 2,2-difluoro-1,5-diketones, 4,4- or 6,6-difluorocyclohexenones, o- or p-fluorophenols, difluoro analogues of terpenes, and difluoro-C-glycosides. (C) 2000 Elsevier Science S.A. All rights reserved.
Umpolung Reactivity of Difluoroenol Silyl Ethers with Amines and Amino Alcohols. Application to the Synthesis of Enantiopure α-Difluoromethyl Amines and Amino Acids
Difluoroenol silyl ethers, produced in situ from acylsilanes and CF3TMS, react as electrophiles with amines to give difluoroimines, via the corresponding hemiaminal adduct, as evidenced by F-19 NMR spectroscopy. Reaction with (R)-phenylglycinol led to 2-difluoromethyloxazolidines. After separation of the diastereomers, reduction with LAH and Strecker-type synthesis gave enantiopure alpha-difluoromethy-lamines and alpha-difluoromethyl-alpha-amino acids, respectively.