Preparation of and Fluoroalkylation with (Chlorodifluoromethyl)trimethylsilane, Difluorobis(trimethylsilyl)methane, and 1,1,2,2-Tetrafluoro-1,2-bis(trimethylsilyl)ethane
作者:Andrei K. Yudin、G. K. Surya Prakash、Denis Deffieux、Michael Bradley、Robert Bau、George A. Olah
DOI:10.1021/ja962990n
日期:1997.2.1
CF2BrCl reacts with aluminum/N-methylpyrrolidinone in the presence of chlorotrimethylsilane to give Me(3)SiCF(2)Cl in high yield. Similarly, CF2Br2 gives Me(3)SiCF(2)Br with bromotrimethylsilane. Chlorodifluoromethylation of aldehydes using Me(3)SiCF(2)Cl and a catalytic amount of TBAF in polar solvents occurs at room temperature, providing difluoromethylated alcohols in two steps. Electroreduction of Me(3)SiCF(2)Cl in the presence of chlorotrimethylsilane gives Me(3)SiCF(2)SiMe(3) (anion-derived product) and Me(3)SiCF(2)CF(2)SiMe(3) (radical-derived product). Using THF/HMPA strongly favors the former, whereas THF/TDA-1 (tris(3,6-dioxaheptyl)amine) the latter. Me(3)SiCF(2)-SiMe(3) difluoromethylates aldehydes acting as a difluoromethylene dianion (''CF22-'' equivalent), whereas Me(3)SiCF(2)-CF(2)SiMe(3) acts at room temperature as an in situ source for the perfluorovinyl anion (due to beta-elimination of fluorotrimethylsilane). However, at low temperature the elimination pathway is suppressed and tetrafluoroethylene dianion (''-CF2CF2-'' equivalent) behavior is observed, The structure of Me(3)SiCF(2)CF(2)SiMe(3) was analyzed by X-ray diffraction. All of the studied fluoroalkylating reagents are moisture- and air-stable and can be readily obtained from a single convenient precursor (CF2BrCl).
Systematic Synthesis of Multifluorinated α,α-Difluoro-γ-lactones through Intramolecular Radical Cyclization
orbital of alpha,alpha-difluoroacetyl radical occurred; this caused unsuccessful cyclization. To apply the present radical reaction, the first synthesis of both enantiomers of difluoroeldanolide, analogues of the sex pheromone of the male African sugarcaneborer, has been demonstrated. Electrophysiological tests revealed that the difluorinated analogues were as active as the natural eldanolide on the