4-Cyclohepten-1 -ones synthesis

W. Pitsch, A. Russel, M. Zabel, and B. Konig, Synthesis of a functionalized cyclohepten-one from erythronic acid-4-lactone, Tetrahedron, 57 (2001) 2345-2347. 

Use of the chiral pool typically requires a series of subsequent transformations to achieve the substitution pattern desired and sometimes may be limited by the availability of only one enantiomer. Microbial oxidations of benzene derivatives have provided an excellent route to cyclohexadienediols in enantiomerically pure form. Although this provides only one enantiomer, synthetic methods have been devised to circumvent this problem [36]. Far fewer methods exist for the enantioselective synthesis of cycloheptenes for which there exists no reaction analagous to the Diels-Alder process [37,38,39,40,41,42]. The enantioselective hydroalumination route to dihydronapthalenols may prove to be particularly important. Only one other method has been reported for the enantioselective synthesis of these compounds microbial oxidation of dihydronaphthalene by P. putida generates the dihydronaphthalenol in >95% ee and 60% yield... 

When Confaione was planning his synthesis of biotin (13), he chose intermediate (14) to supply all the carbon atoms as well as one nitrogen and the sulphur atom. A Michael disconnection gives allylic thiol (15) which can be made from allylic bromide (16) and hence from cycloheptene. 

Irradiation of cycloheptene in the presence of mercury gave a mixture of norcarane, vinylcyclopentane, hepta-1,6-diene, and other minor products. Deuterium labelling showed that the norcarane arose via a 1,2-hydrogen shift followed by ring-closure. The photochemical conrotatory ring-closure of all possible 1,3-dimethyl- and 1,4-dimethyl-cyclohepta-1,3-dienes has been carried out. " ( )-Grandisol has been synthesized from eucarvone, the first step in the synthesis being the photoisomerization of eucarvone to l,4,4-trimethylbicyclo[3,2,0]hept-6-en-2-one. °... 

Ring Expansions. Trost first demonstrated the advantages of methoxy(phenylthio)methane over bis(phenylthio)methane as an acyl anion equivalent in a synthesis of a-methylene-5-lactones via the ring expansion of y-butyrolactones (eq 10). Use of the 0,S-acetal reagent avoided problems encountered with enoliza-tion. Methoxy(phenylthio)methane has also been utilized for the ring expansion of nonenolizable 2-/j-butylthiomethylene cyclohexanones to 3-formyl-2-cyclohepten-l-ones (eq 11). ... 

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