BNC Isosteres of Cyclopropane and a Borylated Diazoester from Diazo Compounds and (Dimethylamino)bis(trifluoromethyl)borane

By “cyclopropanation” with diazo compounds, the first azoniaboratacyclopropane derivatives 2–4 are formed from (CF3)2BNMe2 (1); in these B and N have the coordination number 4. As a result of the CF3 groups 1 reacts like an alkene and not like other aminoboranes. The three ring atoms of the benzyl(trimethylsilyl) derivative 4 form an almost equilateral triangle with the distances BN 1.560(5), BC 1.595(5), and CN 1.567(4)Å.