Scope and limitations of the alkylidene carbene 1,5-CH insertion reactions of α-amino acid-derived substrates

A range of α-amino acid-derived cyclisation precursors were synthesised from suitably protected α-amino esters, via a Dibal-H/Wittig/catalytic hydrogenation strategy and each of these was subjected to alkylidene carbene-forming conditions (lithio(trimethylsilyl)diazomethane, THF). The cyclisations proceeded in poor to good yield, with the best cyclisations occurring to produce spirocyclic products.