| Abstract: | Pivalyl-t-butylmethylene was Generated by the photolysis of 2,2,5,5,-tetramethyl-4-diazo-3-hexanone at T < 22 K. As expected. only one set of triplet signals was observed in the ESR which was assigned to pivalyl-r- butylmethylene, the first alkyl substituted ketocarbene isolated, in the trans conformation. In addition a set of weak, but well-reproducible signals was also observed and it was assigned to the quintet state triplet radical pair. Photolysis of the analogous 3-diazo-2-butanone, however, fails to generate any triplet signal indicating that probably Wolff rearrangement with migration of a methyl and/or 1.2-H shift can compete successfully with ISC from the singlet ketocarbene. |
