The addition of Organolithiums to Ketenethioacetals: A new cyclopentannulation sequence leading to indanes

Article abstract of DOI:10.1016/S0040-4039(00)78885-X

A new cyclopentannulation sequence leading to the rapid preparation of highly substituted indanes e.g. (3) is described. This novel cyclisation protocol is effected via the initial union of an aryl bromide such as (1) with a 2-lithio-2-vinyl-1,3-dithiane e.g. (2) leading to a ketenethioacetal e.g. (4) Transmetallation to the corresponding aryllithium e.g. (5), by addition of an alkyllithium reagent, next effects an intramolecular 5-exo-trig cyclisation onto the ketenethioacetal moiety, leading to an indane intermediate, e.g. (6) Subsequent in situ alkylation of this intermediate (6), with the alkylbromide generated as a consequence of transmetallation, then completes the sequence.