Preparation of seven and larger membered heterocycles by electrophilic heteroatom cyclization

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