Migration aroyl groups

Mattice37 observed the photorearrangement of 3,4-benzocumarin (78) to 4-hydroxyfluorenone (79) with an exceptionally low yield of 0.08% of the initial 78. Here, structural features determine the migration of the aroyl group to the meta-position with regard to the phenolic oxygen atom. For the eventual recombination, the meta-position of a phenoxy radical is extremely deactivated (Table III). 

Aroyl migrations towards primary positions have been observed during the acid-catalyzed removal of acetal groups from 1,2,3,5-tetra-0-benzoyl-4,6-0-ethylidene-D-glucitol587 and 2,4-0-ethylidene-l,3-di-0-(p-nitrobenzoyl)erythritol.588... 

This transformation has been shown (56JA2278) by 14C-labeIling to involve a 1,2-aroyl migration, rather than a 1,2-aryl shift which would necessitate a carbocation intermediate in which the charge is formally adjacent to the carbonyl group (Scheme 167). 

A special case of substitution reaction is the migratory insertion (see Migratory Insertion) reaction of alkyl or aryl metal carbonyls (see equation 58), by which an alkyl or aryl metal carbonyl is converted into an acyl or aroyl metal carbonyl by the action of a Lewis base. This reaction has been studied extensively, and in the case of Mn(Me)(CO)5 is found to proceed through a coordinatively unsaturated tetracarbonyl resulting from methyl migration on to one of the terminal CO groups in a cis position, (see equation 59). ... 

N-Acyl-5 -0-(substituted)trityl nucleosides can be benzoylated or p-methoxybenzoylated selectively at 0-2 . The rate of aroyl migration from O-2 to 0-3 is slower for the anisoyl derivatives, and depends on the exact nature of the 5 -0-protection.243 The removal of the 2,2,2-trichloro-l,l-dimethylethoxycarbonyl (trichloro-t-BOC) group from (184) can be done efficiently using Sn(SPh)3 and tetrabutylammonium cobalt(II)... 

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