Vinyl sulphones, synthesis

Of greater potential practical significance, however, are the note193 and full papers194,195 in which Fabre, Julia and Verpeaux describe a new stereoselective synthesis of trisubstituted alkenes in which vinyl sulphones are attacked by Grignard reagents in the presence of iron or nickel catalysts (equations 82-84). 

Aryl vinyl sulphones, reactions of 646 Aryl vinyl sulphoxides 620 optical resolution of 287 reactions of 354, 355, 360, 361, 621 Asscher-Vofsi reaction 189 Asymmetric induction 625 Asymmetric oxidation 72-78 Asymmetric reduction 78, 79 Asymmetric synthesis 824-846 Atomic orbitals 2, 3 Azetidinones 790, 791 ot-Azidoaldehydes, synthesis of 811 Azidosulphones, photolysis of 883, 884 Azosulphones, photolysis of 879 Azoxysulphones, photolysis of 879 1-Azulyl sulphoxides, synthesis of 265... 

Van t Hoff t-factors 565 Vinylallenes rearrangement of 748 synthesis of 737 Vinyl carbonium ions 620 17a-Vinyl-17/f-hydroxysteroids, epimerization of 735 Vinyl sulphides, as alkyl sulphoxide reduction products 930, 932 Vinyl sulphones - see also Alkenyl... 

Methylenesulphones are more acidic than the simple esters, ketones and cyano compounds and are more reactive with haloalkanes [e.g. 48-57] to yield precursors for the synthesis of aldehydes [53], ketones [53], esters [54] and 1,4-diketones [55] (Scheme 6.4). The early extractive alkylation methods have been superseded by solidtliquid phase-transfer catalytic methods [e.g. 58] and, combined with microwave irradiation, the reaction times are reduced dramatically [59]. The reactions appear to be somewhat sensitive to steric hindrance, as the methylenesulphones tend to be unreactive towards secondary haloalkanes and it has been reported that iodomethylsulphones cannot be dialkylated [49], although mono- and di-chloromethylsulphones are alkylated with no difficulty [48, 60] and methylenesulphones react with dihaloalkanes to yield cycloalkyl sulphones (Table 6.5 and 6.6). When the ratio of dihaloalkane to methylene sulphone is greater than 0.5 1, open chain systems are produced [48, 49]. Vinyl sulphones are obtained from the base-catalysed elimination of the halogen acid from the products of the alkylation of halomethylenesulphones [48]. 

Phase-transfer catalytic conditions provide an extremely powerful alternative to the use of alkali metal hydrides for the synthesis of cyclopropanes via the reaction of dimethyloxosulphonium methylides with electron-deficient alkenes [e.g. 54-56] reaction rates are increased ca. 20-fold, while retaining high yields (86-95%). Dimethylphenacylsulphonium bromide reacts in an analogous manner with vinyl-sulphones [57] and with chalcones [58] and trimethylsulphonium iodide reacts with Schiff bases and hydrazones producing aziridines [59]. 

Rearranged products of type R2YC = CR1R2 are obtained from the vinyl triazene 112 when R2 is an aiyl group and Rx is hydrogen or methyl and also when R2 is tolyl and Rx is phenyl. The acid-catalysed decomposition of vinyl triazene which occurs in very mild conditions has been exploited as a useful method for the synthesis of vinyl sulphonates (Jones and Maness, 1969, 1970 Modena and Tonellato 1971). 

The alkylation of acyclic imines with electrophilic alkenes such as acrylonitrile, methyl acrylate or phenyl vinyl sulphone is also sensitive to steric effects and again, as a consequence, only mono-alkylation occurs398. The regioselectivity of the reaction in methanol varied from 100% attack at the more substituted a-position to 70% attack at the less substituted a -position depending upon the steric inhibition manifested and the stabilization of the competing secondary enamine tautomers (vide infra) (Scheme 204). In contrast, the reaction of butanone and other methyl ketone imines with phenyl vinyl ketone occurs twice at the more substituted a-position but this is then followed by a double cyclization process (Scheme 205). Four carbon-carbon bonds are formed sequentially in this one-pot synthesis of the bicyclo[2.2.2]octanone 205 from acyclic precursors399,400. 

The syntheses by Ban and co-workers of both Na-acetylaspidospermidine (180) and deoxylimapodine (181) (Scheme 32) utilize the important pentacyclic ketone (182), prepared earlier. The critical stage in both syntheses is a Michael reaction, apparently stereospecific, of (182) with methyl vinyl sulphone [-> (180)] and keten thioacetal monoxide [—>(181)], respectively. The later stages in the synthesis are unexceptional. Mercuric acetate oxidation of deoxylimapodine enabled the first synthesis of iVa-acetylaspidoalbidine (183) to be completed. ... 

Reactions of Sulphones.—The first report of pyrolytic elimination of aryl-sulphinic acid from an aryl alkyl sulphone has appeared, for 2-pentyl compounds these give pent-l-ene in constant proportion with cis- and t/ /i5-pent-2-ene, with exceptions for mesityl and p-nitrophenyl 2-pentyl sulphones. Base-catalysed elimination reactions leading to vinyl sulphones are well known, amine-promoted elimination from PhSOzCHa CHF-SPh following a jy/i-stereospecific course through an Elcb mechanism involving ion-pairs. A mild decarbomethoxylative elimination is the last step in a synthesis of ( )-versimide (131). ... 

Studies of jS-alkyl- and -aryl-thio-vinyl sulphonates, mainly from a mechanistic point of view but with implications in synthesis, have been reported in a series of papers. - " j8-Arylthio-compounds (183) give benzo[6]thiophens (184) by cyclization, spontaneously or by BF3... 

Other examples of reactions of [2 + 2] additions of electron-rich and electron-deficient olefins have been reported which are mechanistically similar to those described above. The reaction of p-toiyl vinyl sulphone with enamines gives trans-aminocyclobutyl p-tolyl sulphone (50). The cyclobutyl sulphones (50) are readily cleaved under hydrolytic conditions, presumably via zwitterionic intermediates to the acyclic (51). The reaction is a useful synthesis of a,a-dialkyl-y-sulphone aldehydes. Alkene phosphonates also function as the electron-deficient partner in reactions with enamines. Diethoxyphosphinylethylene reacts with the enamines to give the [2 + 2] adduct (52). The aminocyclobutylphosphonate (52) is stable, but the amine may be eliminated under rather vigorous basic conditions to give the cyclobutenyl-phosphonate (53). 

Books published recently include several that are wholly devoted to organosulphur compoundsand others " in which specific chapters are relevant to the coverage in this chapter. Reviews have appeared that deal with applications of organosulphur compounds in synthesis " (including uses of yff-keto-sulphides, vinyl sulphones, and vinyl sulphides ) and the synthesis of organosulphur compounds,sulphenyl compounds, indolethiols, allenic sulphides and sulphenamides, organosilyl sulphides, selenides, and tellurides, optically active... 

Vinyl sulphones are versatile intermediates for the synthesis of a variety of compounds (e.g.y see ref. 46). Julia et al. have developed a method whereby the a-sulphonyl ketones (176), which are produced by the reaction of the sulphone (175) with esters or with aldehydes followed by oxidation, are converted into ( )- or (Z)-vinyl sulphones, (178) or (179), completely stereospecifically. The a-sulphonyl ketones (176) are reduced with lithio Selectride to give the r/rreu-P-hydroxy-sulphone (177) as the only isomer. Elimination of the tosylate that may be derived from (177) gives the E)- my sulphone (178), whereas analogous elimination of the acetate that is derived from (177) furnishes the (Z)-vinyl sulphone (179). Hsiao and Shechter have prepared a-substituted vinyl... 

CarbocycUc Steroids.— The Torgov synthesis continues to exhibit its great versatility and was recently employed in the first synthesis of B-homo-oestrone. Condensation of the vinyl alcohol (407) and 2-methy 1-cyclopentane-l,3-dione in the presence of l,4-diazabicyclo[2,2 ]octane and cyclisation with toluene-p-sulphonic acid gave the B-homo-oestrapentaene (409) in 33 % overall yield from 3-methoxybenzosuberone. A three-stage reduction by sodium borohydride, catalytic hydrogenation, and lithium-ammonia afforded 3-methoxy-B-homo-... 

Details of an alternative synthesis of 13-methyl-protoberberines have been published. The starting point is an N-phenethyl-homophthalimide of the type (83), and monomethylation is achieved by its Michael addition to methyl vinyl ketone to give the ketone (84 R = H), followed by methylation of this to the intermediate (84 R = M). Conversion of this into the ethylene ketal, followed by reduction with sodium borohydride and heating with toluene-p-sulphonic acid, results in the unsaturated lactam (85), and cyclization of this compound yields the lactam (86), which can be reduced to the 13-methyl-tetrahydroberberine. ... 

The maleopimaric and acrylopimaric adducts, aftCT a three-step synthesis with ethylene glycol catalyzed by p-toluene sulphonic acid (pTS A), followed by epychlorydrine and by acrylic or methacrylic acid, led to the formation of vinyl-type ester monomers (Fig. 4.19), which wctc then submitted to radical copolymerization with styrene and tested as metal coatings [ 103]. A similar approach to coating materials was recently applied to prepare unsaturated polyester resins based on resin acid adducts, glycols and maleic anhydride [104, 105]. 

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