Alkenes from sulfones

A number of methods for the preparation of vinyl and allyl sulfones are available [1U9, 110], and the syntheses of vinyl sulfones from alkenes has been reviewed [116]. A simple one-step procedure of wide applicability makes use of a palladium-catalysed cross-coupling reaction between aryl and alkyl sulfonyl chlorides and substituted vinyl and allyl stannanes... 

Taniguchi N. Stereoselective synthesis of (E)-alkenyl sulfones from alkenes or alkynes via copper-catalyzed oxidation of sodium sulfinates. Synlett 2011 (9) 1308 1312. 

The synthesis of aldehydes via hydroformylation of alkenes is an important industrial process used to produce in the region of 6 million tonnes a year of aldehydes. These compounds are used as intermediates in the manufacture of plasticizers, soaps, detergents and pharmaceutical products [7], While the majority of aldehydes prepared from alkene hydroformylation are done so in organic solvents, some research in 1975 showed that rhodium complexes with sulfonated phosphine ligands immobilized in water were able to hydroformylate propene with virtually complete retention of rhodium in the aqueous phase [8], Since catalyst loss is a major problem in the production of bulk chemicals of this nature, the process was scaled up, culminating in the Ruhrchemie-Rhone-Poulenc process for hydroformylation of propene, initially on a 120000 tonne per year scale [9], The development of this biphasic process represents one of the major transitions since the discovery of the hydroformylation reaction. The key transitions in this field include [10] ... 

Chiral exocyclic alkenes such as 112, also having the chiral center two bonds away from the reacting alkene moiety, have been used in highly diastereoselective reactions with azomethine ylides, and have been used as the key reaction for the asymmetric synthesis of (5)-(—)-cucurbitine (Scheme 12.37) (169). The aryl sulfone 113 was used in a 1,3-dipolar cycloaddition reaction with acyclic nitrones. In 113, the chiral center is located four bonds apart from alkene, and as a result, only moderate diastereoselectivities of 36-56% de were obtained in these reactions (170). 

A similar reaction has been adopted for the preparation of amides from alkenes by the photoaddition of "CONH2 radicals generated from formamide by benzophe-none [7], or via a TBADT [25] photocatalyzed hydrogen abstraction. Solar light has been used in the first case. Furthermore, the introduction of an ester function has been accomplished by generating an alkoxycarbonyl radical by photolysis of [bis(alkoxyoxalyloxy)iodo]benzene at 0-5 °C and ensuing addition to vinyl sulfones in the presence of 1,4-cyclohexadiene [9]. 

Formation of the vinyl sulfone from the B-hydroxy sulfone followed by displacement with a Grignard reagent or cuprate is an alternative to the Julia coupling sequence for trisubstituted alkenes see ref. 272a. 

Conversion of dialkyl sulfones to alkenes either by rearrangement of a-halosulfones with base (via S02 elimination from thiaranedioxides) (Ramberg-Backlund) or by desulfonation of sulfones with BuLi-LAH(Paquette) (see 1st edition). 

Extrapolations of this approach continue to enlarge its usefulness - a,(3-unsaturated sulfones, which can be easily accessed, for example from alkenes by addition of phenylsulfenyl chloride, 5-oxidation and then elimination of hydrogen chloride, have been reacted with isocyanacetates and isocyanonitriles to give pyrroles. 

The disulfonates formation mechanism is complicated and not yet completely clear. Disulfonates in AOS are considered to arise from further sulfonation of alkene sulfonic acids. 

The peroxy intermediate (1) is an excellent reagent for the synthesis of acid-sensitive benzylic epoxides from alkenes, the oxidation of benzylic CH2 to C=0, and the chemoselective oxidation of alkene sulfoxides to alkene sulfones. It is noteworthy that the reactions are carried out under mild conditions (—35 °C). 

Apart from alkene production, n-alkanes are applied as feedstock in the technical production of alkyl sulfonate surfactants (see Section 5.3.5 for details about surfactants and their application). Two routes are established for the production of the alkyl sulfonate sodium salts [R-S03]Na from higher alkanes (for this application typical C-numbers are 12-18). In both routes, alkane activation proceeds via alkyl radicals, which are generated by UV-irradiation at room temperature. In the sulfo-chlorination route, the higher alkane is contacted with SO2 and chlorine to form the alkylsulfonyl chloride, which is later neutralized with NaOH to give the... 

Synthesis of Allylsilanes. TMSCu reacts with a variety of allylic substrates to form allylsilanes stereoselectively and in good to excellent yields. Thus the reagent reacts readily with primary allylic halides, " sulfonates from secondary and tertiary alcohols, and primary and secondary allylic phosphates to yield a variety of allylsilanes. Representative examples of these reactions are shown in eqs 1-3. This methodology seems particularly attractive for the S3Uithe-sis of 3-trimethylsilyl-l-alkenes which are presently unavailable... 

For a long time, the organic chemistry of sulfur dioxide was limited to the formation of sulfinate salts and the sulfones derived therefrom. As shown, the sulfones are highly valuable synthetic intermediates for the construction of carbon-carbon single and double bonds, and very often with high stereoselectivity. More recently, the H-ene and hetero-Diels-Alder reactions of sulfur dioxide have been realized under conditions that avoid polymerization of alkenes, dienes, and other unsaturated compounds. Thus, alk-2-ene-1-sulfonyl chlorides are obtained readily from alkenes... 

Leim W, Herwig J. Palladium-catalyzed hydrosulfenylation synthesis of sulfonic acids and 5-aIkyl alkanethiosulfonates from alkenes, sulfur dioxide, and hydrogen. J. Chem. Soc., Chem. Commun. 1993 1592. 

---