Johnson-Faulkner rearrangement

Johnson, Faulkner, et al.B have developed another approach to synthesis of polyisoprenoids which also utilizes the Claisen rearrangement to establish trans-trisubstituted double bonds. In a model experiment, the allylic alcohol (5) was heated with 7 equivalents of triethyl orthoacetate and 0.06 equivalent of propionic acid at 138° for 1 hour with provision for distillative removal of ethanol the diene ester (6) was obtained in 92% yield. Analysis by vpc indicated that (6) is the trans isomer to the extent of > 98% with less than 2% of the cis isomer. If the classical... 

Trisubstituted C=C bonds. Claisen rearrangement of the /3-hydroxy a-methylene acetals (1) under the conditions of Johnson, Faulkner, ef a/. (3, 301)... 

Johnson WS, Werthemann L, Bartlett WR, Brocksom TJ, Li T-T, Faulkner DJ, Petersen MR. Simple stereoselective version of the Claisen rearrangement leading to trans-tri-suhstituted olefinic bonds. Synthesis of squalene. J. Am. Chem. Soc. 1970 92(3) 741-743. 

This stereoselective version of the Claisen rearrangement leading to tro/is-trisubstituted olefinic bonds has been developed by W. S. Johnson, L. Werthmann, W. R. Bartlett, T. j. Brocksom, T.-t. Li, D. j. Faulkner and M. R. Petersen, J. Amer. Chem. Soc., 92, 741 (1970). The reaction evidently involves formation of a mixed orthoester (i), and loss of ethanol to form the ketene acetal (ii) which rearranges to the olefinic ester (iii). 

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