The cyclization reactions of N-methylpent-4-enylaminyl (10), hex-5-enyl (11) and pent-4-en-1-oxyl (12) radicals were investigated theoretically at the CBS-RAD(B3LYP, B3LYP) level of theory. In all three cases the correspondence between calculated and experimental data was excellent. N-Methylpent-4-enylaminyl (10) is predicted to undergo irreversible (ΔG = −5.4 kcal mol−1; ΔG‡ = 12.1 kcal mol−1) cyclization through the 5-exo manifold. The role of (Bu3Sn)2O in the reactions of arenesulfenamides 6–9 and N-butyl-2-[(phenylselenyl)methyl]pyrrolidine (15) with Bu3SnH in benzene at 80 °C has been reassessed. The purpose of (Bu3Sn)2O in these reactions is to scavenge 2-mercaptobenzothiazole and PhSeH, respectively, which are produced in situ from the reaction of adventitious bis(benzothiazol-2-yl) disulfide and PhSeSePh, respectively, and Bu3SnH. The reaction of N-butyl-2-[(phenylselenyl)methyl]pyrrolidine (15) with Bu3SnH was reinvestigated and found to produce only N-butyl-2-methylpyrrolidine (16) thus confirming the irreversible nature of the cyclization of N-methylpent-4-enylaminyl (10) under the conditions employed in this study.
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