While singlet methylene (1CH2) is known to insert rapidly into CH bonds1 and there is some evidence that it can also insert in C-0 bonds, there is none that it can insert in CC bonds. A recent theoretical calculation2 suggested that insertion into a strained CC bond as in cyclopropane should occur with a small or zero energy barrier, but this has not been confirmed experimentally.3 An upper limit for such a reaction of 1 in 40000 compared with the ...
