PREPARATION OF 7 AND LARGER MEMBERED HETEROCYCLES BY ELECTROPHILIC HETEROATOM CYCLIZATION

The preparation of seven and larger membered ring compounds from linea r substrates is known to be a difficult process, We report results for the preparation of heterocycles with these ring sizes by electrophili c heteroatom cyclizations, Examination of the literature shows that th e obtention of seven-membered compounds is possible in good yields by a proper choice of the electrophilic reagents, while for eight- and la rger membered compounds these cyclisations are possible only if steric constraints are introduced into the chain.