Treatment of α-alkyl and α,α-dialkyl homoallylic amines 1 with PhSeX (X = Cl, Br, I), in CH 3 CN containing sodium carbonate produced mixtures of azetidines 2 and pyrrolidines 3. The cyclization also occurred in the absence of Na 2 CO 3 , and the corresponding azetidinium and pyrrolidinium salts 2(HX) and 3(HX) were formed in CDCl 3 or CH 3 CN. The crude reaction mixtures were analysed by 77 Se NMR. Each product − 2, 3, 2(HX), and 3(HX) − was characterized by its 77 Se chemical shift, and the product ratios were determined for each reaction. The ratios of azetidine 2 to pyrrolidine 3 increased not only according to the steric hindrance around the α-carbon,

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The selenium-induced cyclization of α-alkyl or α,α-dialkylhomoallyl-benzylamines 1 by use of PhSeX (X = Cl, Br, I; 1.5 equiv.) provided a mixture of (phenylselanylmethyl)azetidines 2 and (phenylselanyl)pyrrolidines 3. [1] When an excess of PhSeX (X = Cl, Br) was used, 4-halopyrrolidines 4 (X = Cl) or 5 (X = Br) were formed and isolated in very good yields. Mono-or dialkyl 4-halopyrrolidines 4 and 5 could also be obtained stereospecifically by SO 2 Cl 2 or Br 2 treatment of 4-

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