Synthesis of anti-[ 2 . 2 ] ( 2 . 6 ) benzothiazolo phane via lOn-IOn: coupling protocol

The known 6-methoxymethyl-2-methylbenzothiazole 6 has been converted into quaternary ammonium hydroxide 4 via demethoxy-bromination followed by quaternization with (CH3hN and treatment with silver oxide. Pyrrolysis of 4, expected to generate both anti-l and syn-[2.2](2.6) benzothiazolophane 2 via lOn-I On couplings of the qui nodi methane intermediate 5, gives in practice only anti-benzothiazolophane 1. The structure has been established by comparison with an authentic sample of 1 recently synthesized by an unambigous route.