“…Recently we reported that the stepwise 1,2-dipolar cycloaddition of chlorosulfonyl isocyante (CSI) to alienes [2,4-dimethyl-2,3-pentadiene (6a), 3-methyl-1,2butadiene (6d), pentamethyleneallene (6e) and 1,2-cyclononadiene (6h) ] proceeded via path a to produce initially, in the transition state, an allyl-type stabilized carbonium ion (7) leading ultimately to /3-lactams (8,9) and/or from the aqueous extract, 2-carboxamido-l,3- :oc-c=c: 10 butadienes (10). 6 The reaction between CSI and 6d produced a third product (11) which seemed to be an adduct of 2 equiv of CSI with one of 6d.5 In this paper, we (i) report on CSI addition to alienes 2-methyl-2,3pentadiene (6b), 2,3-pentadiene (6c), 1,3-diphenylpropadiene (6f), and phenylpropadiene (6g); (ii) provide experimental details of the reaction between CSI and 6a-h, with proof of structure of both /3-lactam and diene amide products; (iii) identify 11 by degradation and independent synthesis; (iv) provide experimental evidence for the stereospecific cycloaddition of CSI to cis-and ¿rcms-/3-methylstyrene (cis and trans 16g),6 and…”