Migration acyloxy

The same methodological approach has been extended to the synthesis of biaryls [24]. Reaction (6.12) shows a few examples in which the transfers of functionalized aryl groups from silicon to aryl radicals are successful. A mechanistic scheme similar to that reported in Reaction (6.10) has been proposed. 

2 migration of an acyloxy group in (3-(acyloxy)alkyl radicals has been the subject of numerous synthetic and mechanistic studies [25]. These 

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The 1,2-acyloxy migration in /3-acyloxyalkyl radicals has been the subject of many experimental3 as well as some theoretical studies.4,17 While a broad spectrum of mechanisms is conceivable for this kind of process,3 only three will be discussed here in detail (Scheme 4) (i) stepwise heterolysis/recombination involving... 

Table 2 Activation barriers for 1,2-acyloxy migration in radicals 3a-e through three membered ring transition state 6 and five membered ring transition state 7 (in kJ/mol), and cumulative charge and spin density values for the acyloxy groups as calculated at the UB3LYP/6-31G(d)// UB3LYP/6-31G(d) level of theory14...

Tetrahydrofurans are known to be less conformationally rigid than their 6-membered ring counterparts, and hence anomeric effects in these systems also tend to be less pronounced. In the reactions of 2-tetrahydrofuranyl radicals, stereoselectivities tend to be dictated by steric rather than electronic effects [13]. With respect to C-1 nucleoside radicals, both Tanaka and Chatgilialoglu have independently reported methods for forming these species via 1,2-acyloxy migration and... 

Scheme 16. 1,2-Acyloxy migration in the formation of a-oxygenated nucleoside radicals...

Shu, X., Li, X., Shu, D., Huang, S., Schienebeck, C. M., Zhou, X., Robichaux, P. J., Tang, W. (2012). Rhodium-catalyzed intra- and intermolecular [5 -I- 2] cycloaddition of 3-Acyloxy-l,4-enyne and aUcyne with concomitant 1,2-acyloxy migration. Journal of American Chemical Society, 134, 5211-5221. 

Cycloisomerization of 73 in the presence of copper catalysts and base afforded the corresponding 2,3,5-trisubstituted furans 74 in good to high yields (Scheme 27.27) [37]. The reaction proceeds via prototropic rearrangement to form allene intermediate 75 and subsequent 1,2-acyloxy migration via dioxolenylium intermediate 76. 

Scheme 104 Gold-catalyzed 1,2-acyloxy migration in propargylic carboxylates...

SCHEME 4.18 Gold-catalyzed 1,2-acyloxy migrations of a propargyl carboxylate and the... 

The catalyst-free 5-1-1-cycloaddition reaction between C, A(-cyclic A -acyl azome-thine imines (134) with isocyanides (135) formed imin-l,3,4-oxadiazin-6-one derivatives (136) in high to excellent yields (99%) under mild conditions (Scheme 42). The cobalt-mediated / -pentadienyl (137)/alkyne (138) 5-1-2-cycloaddition reaction yielded /, -cycloheptadienyl complexes (139) under kinetic control. The initial cycloadducts are isomerized to the final >/ -cycloheptadienyl complexes (140) (Scheme 43). The Ru(I)-catalysed intra- and intermolecular 5 4- 2-cycloaddition reactions of 3-acyloxy-l,4-enynes and alkynes produced adducts with highly functionalized seven-membered rings. The reaction sequence includes a 1,2-acyloxy migration. The catalyst-free 5 4- 2-cycloaddition reaction of 2-vinylaziridines with sulfonyl isocyanates in CH2CI2 yielded seven-membered cyclic ureas in high yields (up to 90%). ... 

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