The synthesis of [bis(trifluoromethyl)amino-oxy]-substituted bromoalkanes and their conversion into Grignard reagents

Abstract

Reaction of the nitroxide (CF 3) 2NO· ( 1) with the bromoalkanes RBr (R=Me, Et and Pr n) (1:1 molar ratio) gives the compounds (CF 3) 2NOCH 2Br ( 4a) (69%), (CF 3) 2NOCHBrMe ( 4b) (93%)+(CF 3) 2NOCHBrCH 2ON(CF 3) 2 ( 6) (6%) and (CF 3) 2NOCHBrEt ( 4c) (16%)+(CF 3) 2NOCHMeCH 2Br ( 7) (76%)+(CF 3) 2NOCH 2CHBrMe ( 8) (3%), respectively, together with the hydroxylamine (CF 3) 2NOH ( 3). Treatment of the sodium salt (CF 3) 2NONa ( 2) with the dibromoaikanes Br(CH 2) n Br ( n=2 and 3) (1:1 molar ratio) in diglyme affords mixtures of elimination and substitution products, i.e. H 2CCHBr+(CF 3) 2NOCH 2CH 2Br ( 9a)+(CF 3) 2NOCH 2CH 2ON(CF 3) 2 ( 10a) (ratio 21:39:7) and (CF 3) 2NOCH 2CHCH 2 ( 12)+(CF 3) 2NO(CH 2) 3Br ( 9b)+(CF 3) 2NO(CH 2) 3ON(CF 3) 2 ( 10b) (ratio 22:43:9). The α-substituted compounds 4a and 4b do not form Grignard reagents in diethyl ether, those formed from the β-substituted compounds 7 and 9a undergo elimination to give propene and ethene respectively, while that produced from the γ-substituted compound 9b is stable at room temperature and reacts with the chlorosilane MeSiCl 3 to afford the compound (CF 3) 2NO(CH 2) 3SiCl 2Me ( 20) (53%).