GENERATION AND STUDY OF BENZYLCHLOROCARBENE FROM A PHENANTHRENE PRECURSOR

The curved plots of (carbene adduct)/(carbene-rearrangement product) v ersus carbene trapping agent, tetramethylene [TME], reported with benz ylchlorodiazirine 1 have been reproduced. However, with the use of a n on-nitrogenous precursor, plots of this type are approximately linear over the range of [TME] employed. Thus, any complex formed between ben zylchlorocarbene and TME must collapse to form cyclopropane faster the n it can fragment with rearrangement to beta-chlorostyrene and TME. Di azirine 1 does photoisomerize to diazo compound 7, but this process is inefficient (phi = 0.075) and is not likely to be responsible for the curvature in plots of adduct/styrene versus [TME] observed with the d iazirine precursor. Thus, the second, noncarbene, pathway to beta-chlo rostyrene is neither a carbene-olefin complex nor a diazo intermediate . It is proposed that the second pathway involves a rearrangement in t he excited stale of the diazirine, although other explanations cannot be discarded.