SYNTHESIS OF a-AMINO KETONES AND O-ALKYLOXIMES BY TITANIUM TETRAHALIDE PROMOTED RING-OPENING REACTION OF 2-MONO-SUBSTITUTED AZETIDIN-3-ONES AND THEIR O-ALKYLOXIMES

摘要

Synthesis of a-amino ketones and O-alkyloximes has been developed by titanium tetrahalide-promoted ring-opening reactions of 2-mono-substituted azetidin-3-ones and their O-alkyloximes. Regarding the reductive ring-opening reactions of 2-mono-substituted azetidin-3-ones, an appropriate use of Til4 or TiI4-TiCl4 as a promoter gave a-amino ketones in good yields with high regioselectivities. In TiBr4-promoted ring-opening reactions, while use of 2-mono-substituted azetidin-3-ones as a substrate provided a-amino-a'-bromo ketones generated by the attack of the bromide anion at the less hindered site, those of 2-mono-substituted azetidin-3-one O-alkyloximes proceeded at the more hindered site to give a-amino-a'-bromo ketone O-alkyloximes in good yields.