Glycals allylic rearrangements

Perrier RJ (2001) Substitution-with-Allylic-Rearrangement Reactions of Glycal Derivatives. 215 153-175... 

Tochtermann reported the addition of dichlorocarbene to the racemic glycal 52, whose cyclopropyl-allyl rearrangement leads to the 2//-pyran. The synthesis of the optically pure (+)-(2S,3R,7S) and (-)-(2f ,3S,7f )-glycal precursors has also been achieved. As pointed out, optically pure glycals are versatile precursors for carbohydrate synthesis <00EJO1741>. 

The Lewis acid-mediated allylic rearrangement of glycals like 28 to glycosides 29 known as the Ferrier-reaction is well known in carbohydrate chemistry [14-16]. It yields predominantly a-configurated hex-2-enopyranosides (cf. 29), either in the d-or L-sugar series. These may be hydrogenated to glycosides like the 2,3,6-trideoxy-species 30. 

In order to simplify these preparations, Boivin et al. [52] made use of the allylic rearrangement reaction (Ferrier type) which was one of the first accesses to 3-amino glycals. By use of azide as the nucleophile, the L-arabino configurated glycal 78... 

R. J. Ferrier, Substitution-with-allylic rearrangement reactions of glycal derivatives, in A. E. Stutz (Ed.), Topics in Current Chemistry, Vol. 215, Springer-Verlag, Berlin, 2001, pp. 153-175. 

R. Blattner, R. J. Ferrier, and R. H. Furneaux, Intervention of catalytic amounts of water in the allylic rearrangement of glycal derivatives, Tetrahedron Asymmetry, 11 (2000) 379-383. 

Ferrier, R.J. 2001. Substitution with allylic rearrangement reactions of glycal derivatives. 

Besides nucleophilic substitutions, additions to the double bond of 1,2-unsaturated sugars (glycals) constitute an attractive route for the synthesis of glycosides. Glycals react in these reactions either by a 1,2-addition or by an allylic rearrangement. The following discusses these two reactions in turn. 

A different type of glycosylation reaction of glycals takes place with allyl rearrangement and leads to 2,3-unsaturated glycosides [615]. These glycosylations, often referred to as the Perrier rearrangement, are summarized in Table 4.17. 

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