4382-03-0Relevant articles and documents
Cyclisation of ω-(Isocyanatocarbonyl)alkyl Radicals: Acyclic Precursors of Imidyl Radicals
Kaushal, Parveen,Roberts, Brian P.
, p. 1559 - 1568 (1989)
Imidyl radicals, generated by photolysis of, or halogen-atom abstraction from, N-halogenoimides, are efficiently trapped by But2C=CH2 to give relatively persistent adducts which have been studied by e.s.r. spectroscopy.Bromine-atom abstraction from BrCH2CH2C(O)NCO (2) yields (1) which undergoes rapid 1,5-endo cyclisation to give the succinimidyl radical.This cyclisation has been investigated using e.s.r. spectroscopy in conjunction with spin-trapping by But2C=CH2 and ButN=O.The rate coefficient for cyclisation of (1) has been estimated to be 3.7 * 106 s-1 at 328 K in cyclohexane from analysis of the products from the radical-chain reaction between (2) and triethylgermane.E.s.r. and product-analysis studies show that (14) cyclises, more rapidly than (1), to give the 2,2-dimethylsuccinimidyl radical which subsequently undergoes ring opening to yield (15).The overall rearrangement of (14) to (15) represents a 1,2-shift of the -C(O)NCO group via an intermediate imidyl radical.The glutarimidyl radical is formed by 1,6-endo cyclisation of .It is proposed that the rapid cyclisation of ω-isocyanatoalkyl radicals provides strong evidence that the unpaired electron occupies a ?-orbital in the product imidyl radicals.
