The Synthesis and Chemistry of 9‐Chlorobicyclo[6.1.0]Non‐1(9)‐Ene

Abstract

9‐Chlorobicyclo[6.1.0]non‐l(9)‐ene (4), a 2‐chlorinated 1,3‐fused cyclopropene, is synthesized and isolated from the dehalogenation of the l‐bromo‐9,9‐dichlorobicyclo[6.1.0]nonane, itself derived from cyclooctene. Compound 4 undergoes ring opening reaction to generate cyclooctenyl chlorocarbene (9) which reacts with water via conjugate addition and ipso‐addition to give (E)‐2‐(chloromethylene)cyclooctanol (7) and cyclooctene‐l‐carboxaldehyde (8), respectively. The conjugate addition of 9 with water is more favorable than the ipso‐addition by 3:1. Compound 4, which is stable at −25 °C for weeks without any decomposition, reacts with oxygen to produce 2‐chlorocyclonon‐2‐enone (12) via the ring‐opening reaction adduct, vinyl alkylcarbene 10.

Thermally Induced Cyclopropene−Carbene Rearrangements: An Overview

“…Ring expansion is also reported for the bicyclo[6.1.0]nonene 196 . Reaction with water leads to ( E )-2-chloromethylenecyclooctanol and cycloocten-1-carboxaldehyde, a process claimed to involve the trapping of cyclooctenylchlorocarbene; reaction with oxygen is reported to lead to 2-chlorocyclonon-2-enone, a process reported to involve 2-chlorocyclonon-2-en-1-ylidene . However, no trapping of the carbenes by alkenes is reported, and there are alternative non-carbene processes that may lead to the observed products.…”