Ortho esters, reactions with Grignard reagents

Eliel, E. L. Nader, F. W. Conformational analysis. XX. The stereochemistry of reaction of Grignard reagents with ortho esters. Synthesis of 1,3-dioxanes with axial substituents at C-2.]. Am. Chem. Soc. 1970, 92, 584-590. 

Uncatalyzed nncleophihc snbstitution reactions of Grignard reagents with aromatic compounds is much more difficult than with alkyl species, unless the leaving gronp (sometimes halide nsnally alkoxide is preferred) is activated by one or more potent electron-withdrawing substituents, snch as an oxazoline, nitro, or ester moiety, most often at the ortho... 

Ortho esters have found occasional use as carboxyl blocking groups in some syntheses [73, 74, 75, 76, 96] particularly where it is necessary to prevent reaction at a carboxyl group with a Grignard reagent at a subsequent stage in a synthesis. An example of an application of this type is in the preparation of (57) in studies allied to the synthesis of the antibiotic mycomycin (33) [96]. An alternative use is illustrated by the synthesis of the amino-sugar muramic acid (58) [74]. 

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