Hydroboration of aziridines having a β or γ-double bond 3b, 3c, 4b, 7c and 8 yields after oxidation, the expected hydroxy aziridines 11b, 11c, 12b, 13 and 14, which were cyclized by reaction with PPh3/Br2 to give 1-aza bicyclo [n, 1, 0] alkanes 23b, 24b, 25c, 26 and 27. The hydroboration of 2-vinyl aziridines 3a, 4a and 7a give Z-allylic amines 16aZ, 17aZ and 18Z. The use of 9-BBN or of 2-vinyl substituted aziridines provides the β-hydroxy aziridines 19, ...