Frans-alkene, synthesis

A. Spaltenstein, P.A. Carpino, F. Miyake, P.B. Hopkins, A stereocontrolled synthesis of frans-alkene isosteres of dipeptides. Tetrahedron Lett. 27 (1986) 2095-2098. 

In most cases, a multistep synthesis is not a simple string of reaction steps. You need to look ahead (and behind). For example, you may have a perfectly good reaction that forms a c/s-alkene, but that s the wrong answer because two steps later, you need a frans-alkene. 

B Anti Addition of Hydrogen Synthesis of frans-Alkenes... 

A. Otaka, F. Katagiri, T. Kinoshita, Y. Odagaki, S. Oishi, H. Tamamura, N. Hamanaka, N. Fujii, Regio- and stereoselective synthesis of ( )-Alkene frans-Xaa-Pro dipeptide mimetics utilizing organocopper-mediated Anti-S M2 reactions, J. Org. Chem. 

X.J. Wang, S.A. Hart, B. Xu, M.D. Mason, J.R. Goodell, F.A. Etzkorn, Serine-c/s-proline and Serine-frans-proline isosteres Stereoselective synthesis of (Z)- and ( )-alkene mimics by still-wittig and ireland-claisen rearrangements, J. Org. Chem. 

C.Y. Cheng, B.l. Liou, S.T. Jih, Stereoselective synthesis of frans-( )-A/- 2-[4-(3,4-dichlorophenyl)but-2-en-2-yl]cyclohexyl pyrrolidine as an alkene mimetic of the aryla-cetamide analgesics, J. Chinese Chem. Soc. (Taipei, Taiw/an) 40 (1993) 67-71. 

Since reactivity of alkenes increases with increasing alkyl substitution, hydration is best applied in the synthesis of tertiary alcohols. Of the isomeric alkenes, cis compounds are usually more reactive than the corresponding trans isomers, but strained cyclic isomeric olefins may exhibit opposite behavior. Thus, for example, frans-cyclooctene is hydrated 2500 times faster than cw-cyclooctene.6 Similar large reactivity differences were observed in the addition of alcohols to strained trans cycloalkenes compared with the cis isomers. frans-Cycloheptene, an extremely unstable compound, for instance, reacts with methanol 109 faster at —78°C than does the cis compound.7... 

Z58 It is sometimes necessary to isomerize a cis alkene to a trans alkene in a synthesis, a process that cannot be accomplished in a single step. Using the reactions you have learned in Chapters 8-12, devise a stepwise method to convert c/s-2-butene to frans-2-butene. 

In the laboratory of S. Kumar, the synthesis of phenolic derivatives of frans-7,8-dihydroxy -7,8-dihydrobenzo[a]pyrene, a highly tumorigenic compound, was accomplished. The frans-vicinal diol functionality was introduced by using the "dry" Prevost conditions. The alkene was subjected to a mixture of iodine and silver benzoate in dry refluxing benzene to give a good yield of the corresponding frans-7,8-dibenzoate derivative. 

In the last 15 years we have developed two new catalytic reactions between the same parent substances, i.e. silylative coupling (SC) (also called frans-silylation or silyl group transfer) and cross-metathesis (CM) of alkenes, which have provided an universal route for the synthesis of well-defined molecular compounds with vinylsilicon functionality. While the cross-metathesis is catalyzed by well-defined Ru and Mo carbenes, the silylative coupling is catalyzed by complexes initiating or generating M—H or M-Si bonds (where M = Ru, Rh, Ir). For recent reviews see Refs. [4-6]. 

When an alkene is reacted with the peroxy acid (1) In aqueous acetone, the anti hydroxylation product is obtained direcdy. Cyclohexene (8) is converted to the trans-dioX (9) (eq 3). Reagent (1) has been used for the synthesis of ( ) y-rhodomycinone (11) via frans hydroxylation of the alkene (10) (eq 4). ... 

Natural Cyclopropanes.—In extensions of their earlier investigations of the synthesis of chrysanthemic acid (25) based on elaboration of the cyclopropane ring by reaction between the isopropyl ylide (22) and alkene substrates (see Volume 1, p. 292), Krief and his co-workers have now shown that the ylide (22) can be added to both maleate and fumarate, leading to the frans-cyclo-propanedicarboxylate (23). Conversion of the diester into the aldehydo-ester (24) and Wittig reaction then completes a new synthesis of chrysanthemic acid (Scheme 5). 

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