Synthesis of quaternary α-benzyl- and α-allyl-α-methylamino cyclobutanones

A simple and practical protocol for the construction of synthetically important quaternary α-benzyl- and α-allyl-α-methylamino cyclobutanones in good to high yield, via a sequential one-pot methylation/sigmatropic rearrangement, has been accomplished for the first time. The quaternary α-alkyl-α-amino cyclobutanones could be further manipulated, affording synthetically interesting scaffolds such as highly substituted tryptamines and cyclobuta-fused indolines.