ATTACK BY RADICALS OR ELECTRON DEFICIENT SPECIES

Surprisingly little is known about the attack of radicals on small and large heterocycles. Hydrogen abstraction from the heteroatom of small rings leads to ring opening, and in the 

Thiiranes are desulfurized by radicals (H, S-)i by singlet carbenes and by electrolysis (Section 5.06.3.7.1). 

Saturated large rings may form nitrogen radicals by H abstraction from N, or abstraction may occur in the a- or /3-positions in nonnitrogen systems. Oxepane gives the radical in the 2-position, with subsequent cleavage and reclosure of the intermediate carbenoid to cyclohexanol (Section 5.17.2.1.5). In unsaturated large systems a variety of reactions, unexceptional in their nature, are found. Some azepines can be brominated by A -bromosuc-cinimide others decompose under similar conditions (Section 5.16.3.7). 

Electron deficient species can attack the unshared electron pairs of heteroatoms, to form ylides, such as in the reaction of thietane with bis(methoxycarbonyl)carbene. The S —C ylide rearranges to 2,2-bis(methoxycarbonyl)thiolane (Section 5.14.3.10.1). A -Ethoxycar-bonylazepine, however, is attacked by dichlorocarbene at the C=C double bonds, with formation of the trans tris-homo compound (Section 5.16.3.7). 

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ATTACK BY RADICALS OR ELECTRON-DEFICIENT SPECIES. OXIDATION AND REDUCTION 489... 

Attack by Radicals or Electron-Deficient Species. Oxidation and... 

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