Unusual reactivity of lithiated 2‐alkylbenzotriazoles

Treatment of a 2‐alkylbenzotriazole (BtCH2R) (2) with LDA at −78°C produces rapidly a mixture of a coupling product (BtCHR–CHRBt) (5) and a compound formed from four molecules of the starting material (BtCHR–CHR–CHR–CHRBt) (6). A mixture of 2‐methylbenzotriazole and benzophenone, treated with LDA, gives adduct Ph2C(OH)CH2Bt (14) quantitatively whereas benzaldehyde does not react under these conditions. 2‐Alkylbenzotriazoles (2) are alkylated at the α‐carbon atom when their mixtures with alkyl halides are treated with LDA. magnified image