Hydro-de-acylation

Basic Cleavage of P-Keto Esters and p-Diketones Hydro-de-acylation... 

See G. Mehta, R. V. Venkateswaran, Tetrahedron 2000, 56, 1399. In this updated Review, the authors indicate the inclusion of alkoxide cleavages as Haller-Bauer. March describes these as "Hydro-de-Acylation" reactions. See also M. B. Smith, J. March in March s Advanced Organic Chemistry, 5th ed., John Wiley and Sons, Inc., New York, 2001, p. 814 K. E. Hamlin, A. W. Weston, Organic Reactions 9, 1. 

Unlike alkylation, Friedel-Crafts acylation has been generally considered to be irreversible, but a number of instances of electrofugal acyl groups have been reported, especially where there are two ortho substituents, for example the hydro-de-benzoylation of 42. ... 

Acylations of lithium enolates of JV-acyloxazolidinones 5.30 and 5.31 by acetyl or benzoyl chloride at -78°C are highly diastereoselective (de > 90%) [167]. Such is also the case for reactions of Samp or Ramp 1.76 hydrazone enolates with CICOOMe [1077] or MeNCS [1078], Sodium enolates of iV-acyloxazolidinones 5.30 and 5.31 can be oxidized on the least hindered face at -78°C by an oxaziridine [741], After cleavage of the chiral auxiliary by magnesium methoxide, a-hydro-xyesters are obtained with an excellent enantiomeric excess [742] (Figure 5.39). Similar results are obtained from Samp and Ramp 1.76 hydrazone enolates [742] (Figure 539). Oppolzer and coworkers [147] carried out the stereoselective... 

Conjugate addition products 322 and 323 have been subjected to hydro-genolysis in the presence of 10% Pd/C catalyst (Scheme 4.103). " 3-Substituted coumarins 324 were obtained in 50-66% yields from substrates 322 through fission of the benzyl ether and spontaneous cyclization via acyl substitution. Using compounds 323 as substrates, piperidinyl derivatives 325 were obtained in 45-61% yields, and the de-aminated derivatives 326 were also acquired in 9-21% yields. Such a synthetic method may enable the synthesis of multi-substituted coumarins (2//-l-benzopyran-2-ones), which are widely distributed in nature and many of which exhibit pharmacological activities. 

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