(95) Bifurcated synthesis of methylene-lactone- and methylene-lactam-fused spirolactams via electrophilic amide allylation of γ-phenylthio-functionalized γ-lactams
Tetsuya Sengoku, Koki Makino, Ayumi Lijima, Toshiyasu Inuzuka and Hidemi Yoda
Beilstein Journal of Organic Chemistry,  2020, 16, 2769–2775. (DOI: 10.3762/bjoc.16.227) 

New synthetic methods for spirolactams bearing an α-methylene-γ-butyrolactone or its analogous methylene-lactam have been developed.