An efficient and a facile route to spiro-𝛽-lactams is described. 3-allyl-3-methylthio-𝛽-lactams, which are synthesized through a Lewis acid mediated C-3 alkylation of the trans-3-chloro-3-methylthio-𝛽-lactams, undergo a facile intrasulfenyl cyclization reaction in the presence of halogens like bromine and iodine to give spiro 𝛽-lactams in good yield. These halospiro-𝛽-lactams are then subjected to dehalogenation reaction using Raney-nickel. The resulting spiro-𝛽-lactams are further transformed into their sulfinyl and sulfonyl derivatives by using 𝑚-chloroperbenzoic acid as an oxidant.

An effective and stereoselective synthesis of 3-(1'-methyl/phenylallyl)-3-phenylthio-β-lactams (3/4) using substituted allylsilane and Lewis acid is described. The reaction leads to the formation of a mixture of C-3 substituted allyl β-Lactams. However, these compounds on desulphurisation using tri-n-butyltinhydride and Raney Ni provide two separable diastereomers of the reduced product.