Alkylation of dimethylaminobis(trifluoromethyl)borane by 1-alkenes

Abstract

Dimethylaminobis(trifluoromethyl)borane, (CF 3) 2BNMe 2 ( A), undergoes B-alkylation on treatment with 1-alkenes of the general formula (R 1CH 2)(R 2)CCH 2 to yield triorganoboron adducts Me 2(H)NB(CF 3) 2CH 2(R 2)CCHR 1(R 1 H, R 2Me ( I); R 1H, R 2  CH 2(CF 3) 2BNHMe 2 ( II); R 1Me, R 2 Et ( III); R 1H, R 2CH 2( tBu) ( IV); R 1H, R 2Ph ( V); R 1H, R 2 CHCMe 2 ( VI); R 1Ph, R 2H ( VII); R 1 nPr, R 2H ( VIII); R 1 iPr, R 2H ( IX)). In contrast, monosubstituted ethene derivatives (R 2)CHCH 2(R sBu, Ph, Mes, Me 3Si, Et 3Si) react with A to form the corresponding methylmethyleneimine boron adducts H 2CN(Me)B(CF 3) 2CH 2C H 2R 2 ( X, XII–XV). With ( tBu)(Me)CCH 2, A undergoes both types of reaction, yielding a 1/4 mixture of Me 2(H)NB(CF 3) 2CH 2 ( tBu)CCH 2 ( XIa) and H 2CN(Me)B(CF 3) 2CH 2CH(Me)( tBu) ( XIb). Whereas I–IX and XIa are formed by an ene-type reaction, X and XIb–XV result from a shift of a hydride from the dimethylamino group to the alkylating substituent. The novel boranes have been characterized by elemental analysis and multinuclear NMR, IR and mass spectroscopy.