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N-vinyl-, N-allyl-, N-propenyl- And N-propargyl-benzotriazoles : Reactions Of Their Lithium Derivatives
Published 1992 · Chemistry
1-Vinylbenzotriazole undergoes lithiation at the α-carbon and subsequent reactions with electrophiles to afford 1-(1-substituted vinyl)benzotriazoles (3a–d). Similarly, 1-(1-substituted propenyl)- (9a–c, 9e, 10a–c, 10e) and 2-(1-methylpropenyl)-benzotriazoles (14 and 15) were prepared by lithiation of the corresponding 1- and 2-propenyl-benzotriazoles followed by alkylation. 1- and 2-Allylbenzotriazoles 4 and 5 are also lithiated at the α-carbon and the intermediates react with electrophiles at this position. The structures of the propenyl derivatives were supported by an alternative synthetic route via rearrangements of the corresponding allyl isomers. 1-Propargylbenzotriazole (16) undergoes lithiation first at the acetylenic CH and then at the CH2 group. The dilithiated species, produced by treatment of 16 with two equivalents of butyllithium, reacts with an electrophile first at the carbon atom adjacent to the nitrogen atom, and then at the terminal carbon atom. Hence lithiation of 16 and subsequent reactions with electrophiles afford alkylated products 17a–d, 18a–d, 19a–b and 20a–c depending upon the amount of butyllithium and of the electrophile(s) used. The structures of each class of product were supported by spectral and analytical data.