Rearrangement Meinwald

Scheme 8.6. Asymmetric ester hydrolysis followed by Meinwald rearrangement.

This particular type of Wagner-Meerwein shift has special recognition due to its importance in the field of terpene chemistry. For example, the conversion of a-methylcamphene into 4-methylisoborneol involves both a Nametkin and a Wagner-Meerwein rearrangement. In the Meinwald rearrangement both 1,2- and 1,3-shifts occur to give different products (Scheme 2.24). 

Other references related to Meinwald rearrangement are cited in the literature. ... 

An extraordinarily simple approach to a Fischer indoli-zation is that of Taylor and Donald [120] involving the transformation of epoxides to indoles via aldehydes or ketones (the Meinwald rearrangement) in the presence of arylhydrazines, and thence to indoles, obviating the need for isolating the carbonyl compound. Selected examples of this simple chemistry are shown in Scheme 18 (equations 1, 2). Of the Lewis acids screened, scandium(III) triflate proved to be superior. Greaney and colleagnes... 

Patil et al. found that the benzannulation of o-alkynylbenzaldehydes 11 with styrene oxides 54 proeeeded in the presence of h (Scheme 15.22) [35]. Probably, styrene oxides would undergo Meinwald rearrangement to form enols, which would participate in [4 -t- 2] cycloaddition with pyrylium intermediates. 

An a-hydroxy-spiro epoxide has been reported to undergo a tandem/Meinwald rearrangement to give a cyclopentyl hydroxymethyl ketone with Lewis acid (Scheme 58)7 ... 

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