Esters 1- cyclopropyl propargylic

SCHEME 17.22 Rhodium-catalyzed synthesis of cyclohexe-nones from cyclopropyl propargyl esters. 

A gold(I)-catalysed homo-Rautenstrauch rearrangement of 1-cyclopropyl propar-gylic esters to cyclohexenones is considered evidence for the gold-stabiUzed nonclassical carbocation character of intermediates. A mechanistic study revealed 0 partial chirality transfer from optically active propargyl acetates (Scheme 125). 

In the case where the initial propargylic ester bears a cyclopropyl group, the formation of the allene intermediate 192 is followed by ring opening of the three-membered ring to lead to the cation 193 that cyclizes into alkylidene cyclopentenyl acetates 194 (Scheme 79) [167]. 

Another type of cyclopropyl substituted propargyl esters (101) with acyloxy placed between the cyclopropane and the alkyne can also undergo the transformation (Scheme 17.24). To diminish the formation of triene by-products, 10 atm of CO had to be used. 

Two different types of tandem reactions for the synthesis of highly functionalized cyclohexenones cyclopropyl-substituted propargyl esters initiated rhodium-catalysed Saucy-Marbet 1,3-acyloxy migration have been reported (Scheme 152). The resulting cyclopropyl-substituted allenes derived from acyloxy migration followed by 5 -f 1-cycloaddition with carbon monoxide. ... 

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