The chemistry of cyclopropylidenes. Part 1. Reaction of 7,7-dibromo-3-vinylbicyclo[4.1.0]heptanes with methyl-lithium

Abstract

Reaction of anti-7,7-dibromo-3-vinylbicyclo[4.1.0]heptane (10) with LiMe, prepared from Mel and Li, leads at 25–35 °C to products derived by insertion of a cyclopropylidene into the C₃–H and C₅–H bonds, and to insertion into, the solvent ether. At –40 to –50 °C, the intramolecular insertion products are replaced by exo-7-iodo-3-vinylbicyclo[4.1.0]heptane (29).

Reaction of syn-7,7-dibromo-3-vinylbicyclo[4.1.0]heptane with LiMe at 25–35 °C leads to a second iodide. (17) but at –40 to –50 °C gives a spiro-derivative (28). The latter is converted to (17) with Lil·H₂O at 25 °C and reacts exothermally with MeOH and AcOH; it rearranges on g.l.c. or on reaction with Ag⁺–C₆H₆ to (37) which on hydroxymercuration leads to (38).