Ramberg-Backlund olefin synthesis

Olefin synthesis by treatment of an a-halosulfone with base. 

Ramberg, L. Backlund, B. Arkiv. Kemi, Mineral Geol. 1940, 13A, 50. 

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RAMBERG BACKLUND Olefin Synthesis Conversion of dialkyl suNones to akenes by rearra/tgement of a-haiosulfones with base (via imaranedloxfdes). 

Chen, T. B. R. A., Burger, J. J., De Waard, E. R. The Michael induced Ramberg-Backlund olefin synthesis. Tetrahedron Lett. 1977, 4527-4530. 

Li, J. J. Ramberg-Backlund olefin synthesis. In Name Reactions for Functional Group Transformations , Li, J. J., Corey, E. J., Eds. John WUey Sons Hoboken, NJ, 2007, pp 386-404. (Review). 

The reaction of halogenomethylvinylsulphones with sulphinate anions, termed the Michael-induced Ramberg-Backlund olefin synthesis, represents an interes-... 

An efficient strategy for the synthesis of /raor-fused oxabicyclic systems involving this annulation followed by a Ramberg-Backlund olefination (Equation 47) as the key step is used for the ring contraction of 116 to give the oxepane 117 in 41% yield, in which the intermediates formed on a-chlorination and sulfone formation steps were used without purification <1996TL2865>. 

PAQUETTE Olefin Synthesis OesuHonatlon of suHones to alkenes (altemative to Ramberg-Backlund). 

There have been Ramberg-Backlund-type reactions in which the leaving group is not a halide ion. For example, treatment of the polyalkylated methyl triflone 365 is known to result in a Ramberg-Backlund reaction forming the corresponding olefin. Since methyl triflone 364 can be alkylated successively regiospecifically at the two carbon atoms, Hendrickson and coworkers used this reaction for the synthesis of some tailor-made olefins. 

Similarly, starting from 2,3 5,6-di-0-isopropylidene-D-mannofuranose 72, a one-pot procedure that implies the synthesis of glycosyl sulfones by Horner-Wadsworth-Emmons olefination with phosphonate 73, followed by subsequent Michael addition and Ramberg-Backlund reaction92 gives compound 74 in 78% yield93 (Scheme 24). 

Becker, K. B., Labhart, M. P. The intramolecular Ramberg-Backlund reaction a convenient method for the synthesis of strained bridgehead olefins. Heiv. Chim. Acta 1983, 66,1090-1100. 

In 1977, de Waard at the University of Amsterdam conceived and prosecuted a novel approach that he dubbed the Michael-induced Ramberg-Backlund (MIRB) olefin synthesis. 24,25 The reaction of dienyl sulfone 25 with one equivalent of sodium phenylsulfinate produced the Michael-induced Ramberg-Backlund product 26 in 40% yield. 

In a formal total synthesis of steroid brassindole, sulfide 102 was used as the substrate of the Ramberg-Backlund reaction.57 Chlorination of 102 followed by oxidation with m-CPBA, and treatment of the resulting chloro-sulfone with potassium t-butoxide, provided symmetrical olefin 103. 

Hart assembled olefin 109 convergently from benzyl bromide 106 by taking advantage of the Ramberg-Backlund reaction.59 As depicted below, the Sn2 displacement of benzyl bromide 106 with thiol 107 led to sulfide 108. Oxidation of 108 to the sulfone, followed by the Myers modification delivered alkene 109, an intermediate for the synthesis of C-aryl glycosides related to chrysomycins. 

PAQUETTE Olefin Synthesis Desulfonation o( sutfones to alkenes (alternative to Ramberg-Backlund). 

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