Tetrahedron Letters No. 8, pp zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 577 - 580, 1974. Per&amonPress. Printed in Great Britain. A FACILE PHOTOCHEMICALLY INDUCED ARYLCARBENE- AROMATIC CARBENE REARRANGEMENT IN SOLUTION Udo H. Brinker and W. M. Jones Department of Chemistry, University of Florida, Gainesville, Florida 32611 (Receivedin US% 3 November 1995; receivedin UK ior publication 15 Jenuary 1976) The interconversion of aryl and aromatic carbenes has been explored in both the gas phase' and solution1'2. In the latter medium, a number of aromat- ic carbenes have been found to convert to their aryl counterparts at modest temperatures 3 but, to date, only one example of a solution phase rearrangement of an arylcarbene to its aromatic counterpart has been recorded' and in this case, the rearrangement only occurred upon thermal decomposition of the cor- responding tosylhydrazone salt. At this time we report the low temperature (as low as -70°) carbene-car- bene rearrangement of the methanoannulenylcarbene 5 to one of its two - isomeric methanoannulenylidenes 7. - This constitutes the first example temperature rearrangement of an arylcarbene to an aromatic carbene, a which is remarkable not only for its facility but for its high degree specifity. possible of a low reaction of regio- 597