SYNTHESIS AND REACTIONS OF LITHIO DERIVATIVES OF 1-ALLENYLBENZOTRIAZOLE

1-(2-Chloropropen-2-yl)benzotriazole (6) is converted by heating with sodium hydroxide or by lithium diisopropylamide at -78-degree into 1-allenylbenzotriazole (1) in high yield. Allene 1 undergoes in situ lithiation at the alpha-carbon and subsequent reactions with iodomethane or carbonyl compounds to produce 1-(1-substituted allenyl)benzotriazoles 9 and 2a-c, respectively. Three equivalents of lithium diisopropylamide dilithiated 1 and afforded symmetrical 1-(1,3-disubstituted allenyl)benzotriazoles 11a,b upon reaction with ketones. The unsymmetrical 1-(1,3-disubstituted allenyl)benzotriazole 5 was obtained via a stepwise addition of benzophenone to the lithio derivative of 1 followed by a second lithiation and quenching with acetone. Monosubstituted allenes 2a and 8 were cyclized into the benzotriazolyl substituted dihydrofuran 3 and dihydropyrrole 4 respectively.