Isomerizations potassium ferf-butoxide

Pinocarveol has been prepared by the autoxidation of a-pinene,5 by the oxidation of /S-pinene with lead tetraacetate,6 and by isomerization of a-pinene oxide with diisobutylalumi-num,7 lithium aluminum hydride,8 activated alumina,9 potassium ferf-butoxide in dimethylsulfoxide,10 and lithium diethylamide.11 The present method is preferred for the preparation of pinocarveol, since the others give mixtures of products. It also illustrates a general method for converting 1-methylcy-cloalkene oxides into the corresponding exocyclic methylene alcohols.11 The reaction is easy to perform, and the yields are generally high. 

An equilibrium between the isomeric hydroxysulfones, VIII/44 and VIII/45, was observed in the presence of butyllithium. Treatment of VIII/44 with potassium ferf-butoxide gave only the ring enlarged (E)-isomer VIII/46. The ( -configuration of the double bond is the result of the stereoelectronic course of the fragmentation. Under the same reaction conditions the formation of the isomeric VIII/47 from VIII/45 was not observed only compound VIII/46 was isolated. This must happen via thermodynamically controlled epimerization of VIII/45 —> VIII/44. For similar reactions, see ref. [28]. 

Write structural formulas for all the products that would be obtained when each of the following alkyl halides is heated with potassium ferf-butoxide in terf-butyl alcohol. When more than one product results, you should indicate which would be the major product and which would be the minor product(s). You may neglect cis-trans isomerism of the products when answering this question. 

On the basis of this palladium-mediated Michael addition cyclization process, a novel two-step synthetic entry into functionalized furan derivatives 67 has also been devised (Scheme 28). Substitution of benzylidene (or alkyli-dene) malonates for their ethoxymethylene analog (65) as activating olefins gave rise to the formation of the corresponding 2-ethoxy-4-arylidene tetrahy-drofurans 66. An in situ addition of potassium ferf-butoxide induced a decar-boxylative elimination reaction which was followed by an isomerization of the exocychc double bond. The entire process successively involved a conjugate addition, a palladium-catalyzed cycHzation-coupling reaction, a base-induced eliminative decarboxylation, and finally, a double bond isomerization (73). 

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