Frans-3-PENTEN-2-ONE

Robinson annelation. Robinson annelation of substituted cyclohexanones with the reagent offers an entry into eremophilone-type sesquiterpenes. Thus the total synthesis of ( )-nootkatone (2) has been achieved by the annelation of (1) with frans-3-pentene-2-one in the presence of sodium hydride.3 In this case only one isomer was isolated. However, Coates and Shaw4 noted that the steric outcome of... 

In connection with potential routes to sesquiterpenoids of the eremophilane and valencane classes, Marshall and Ruden have found that acid-catalysed cleavage of the cyclopropyl ketone (284) gives exclusively the enone (285). This is in contrast to the epimeric ketone (286) which yields predominantly (287). Leitereg has found that Robinson annelation of (-H )-dihydrocarvone with frans-3-penten-2-one gives as a major compound the bicyclic enone (288) which is isomeric with (-f- )-nootkatone (242). The full paper on the structures of a- (289) and j -rotunol (290) has been published. 

Van Ruth et al. (1995) described the flavour components in bell peppers. Out of 47 compounds identified, 12 could be detected by assessors at a sniffing port on a gas chromatograph. 3(2220) 2-Methylpropanal,9 2-methylbutanal, 10 3-methylbutanal, 13(2370) 2,3-butanedione, 15(3382) l-penten-3-one, 19(2557) hexanal, 25(2540) heptanal, 29 P-ocimene, 35 frans-3-hepten-2-one, 39 dimethyltrisulphide, 45(3132) 2-isobutyl-3-methoxypyrazine and 47(3639) P-cyclocitral were the major compounds. 

Dr. Brill One would expect frans-2-butene-l-hydroperoxide to be the more stable isomer and the one formed in largest quantity by rearrangement of l-butene-3-hydroperoxide. In a previous study, only trans-2-methyl-3-pentene-2-hydroperoxide was obtained by equilibration with its allylic isomer. 

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