To unsaturated sulfones

TABLE 5. Survey of sulfonyl halide additions to unsaturated systems and hydrogen halide eliminations to unsaturated sulfones... 

The conjugate addition of tributylstannylmethyllithium to unsaturated sulfones 100, followed by trapping with an aldehyde, provides a route to the allyl alcohol 101 which may be transformed into 2(5H)-furanones (equation 81)67. 

The Julia-Colonna epoxidation uses poly-L-leucine and hydrogen peroxide to effect enantioselective epoxidation of chalconc derivatives such as 12. In a pair of back-to-back papers (Tetrahedron Lett. 2004,45, 5065 and 5069), H.-Christian Militzer of Bayer Healthcare AG, Wuppertal, reports a detailed optimization of this procedure. In the following paper (Tetrahedron Lett. 2004,45,5073), Stanley Roberts of the University of Liverpool reports the extension of this procedure to unsaturated sulfones such as 14. 

After conversion to unsaturated sulfonates through reaction with vinyl or allyl sulfonyl chlorides, both primary and secondary alkenols afford dihydro-1,2-oxathiane 2,2-dioxides through a Ru-catalysed RCM (Scheme 55) <06T9017>. 

Synthesis of (—)-Sibirine. Various types of alkaloids have been prepared by conjugate addition of carbon-centered radicals to unsaturated sulfones. This approach is used in the stereoselective synthesis of the Nitraria spirocyclic alkaloid (—)-sibirine, where a 6-exo-trig radical cyclization to an a,(3-unsaturated sulfone leads to the spirocyclic skeleton of the natural product (Eq. 153).263 The y-nitrogen-functionalized sulfone so obtained is then desulfonylated under dissolving-metal conditions. 

Another way to place negative charge into the a-position of the sulfone group results from conjugate addition to unsaturated sulfone derivatives 529-533 represent the most important ones in this group. 

The Barton-Zard (BZ) pyrrole synthesis is similar both to the van Leusen pyrrole synthesis that uses Michael acceptors and TosMlC (Section 6.7) and the Montforts pyrrole synthesis using a,P-unsaturated sulfones and alkyl a-isocyanoacetates." An alternative to the use of the reactive nitroalkenes 1 is their in situ generation from P-acetoxy nitroalkanes, which are readily prepared via the Henry reaction between an aldehyde and a nitroalkane followed by acetylation. Examples are shown later. 

The addition of methyllithium to -alkoxy-a-(trimethylsilyl)-of/ unsaturated sulfones, 3-alkoxy-5-phenyl-l-phenylsulfonyl-l-(trimethylsilyl)-l-pentene and subsequent desilylation gives syn-products. The syn to anti diastereoselectivity is generally high and essentially independent of the nature of the y-alkoxy substituent8-13. 

In contrast cyclic y-(rey/-butyldimethylsilyloxy)-a,/ -unsaturated sulfones undergo addition of organometallic reagents to give mainly trans-adducts after reductive removal of the sulfonyl group. 

The diastereoselective addition of [(S)-3-alkoxy-l-octenyl]lithium to an enantiomerically pure cyclic y-(rer/-butyldimethylsilyloxy)-o(,/S-unsaturated sulfone was employed in the synthesis of ( )-prostaglandin E219, with addition occurring exclusively anti to the sterically demand-... 

Addition of methyllithium to a cyclic /i, y -epoxy-a,/i-unsaturated sulfone gave predominately the m-alcohol as product20. 

The addition of a lithiated dithiane to a chiral a,/J-unsaturated sulfone has been reported, however, the stereochemical outcome and the diastereoselectivity was not addressed20. The addition of (lithiomcthylsulfonyl)benzenc to a chiral y-alkoxy-a-trimethylsilyl-aj-unsaturated sulfone gave exclusively the, vr -adduct1 2 3 4 5 7 8 9 10 11 12. 

B. Radical Addition of Sulfonic Acid Derivatives to Unsaturated Systems. 189... 

Besides radical additions to unsaturated C—C bonds (Section III.B.l) and sulfene reactions (see above), sulfonyl halides are able to furnish sulfones by nucleophilic substitution of halide by appropriate C-nucleophiles. Undesired radical reactions are suppressed by avoiding heat, irradiation, radical initiators, transition-element ion catalysis, and unsuitable halogens. However, a second type of undesired reaction can occur by transfer of halogen instead of sulfonyl groups283-286 (which becomes the main reaction, e.g. with sulfuryl chloride). Normally, both types of undesired side-reaction can be avoided by utilizing sulfonyl fluorides. 

In order to justify the validity of ketone-sulfone analogies, a series of CNDO/2 calculations on a number of model cyclic unsaturated sulfones and ketones was... 

An illustrative example of the Michael reaction is that of the thiirene dioxide 19b with either hydroxylamine or hydrazine to give desoxybenzoin oxime (87) and desoxybenzoin azine (88), respectively, in good yields6 (see equation 29). The results were interpreted in terms of an initial nucleophilic addition to the a, j8-unsaturated sulfone system, followed by loss of sulfur dioxide and tautomerization. Interestingly, the treatment of the corresponding thiirene oxide (18a) with hydroxylamine also afforded 86 (as well as the dioxime of benzoin), albeit in a lower yield, but apparently via the same mechanistic pathway6. 

As formal a, /i-unsaturated sulfones and sulfoxides, respectively, both thiirene dioxides (19) and thiirene oxides (18) should be capable, in principle, of undergoing cycloaddition reactions with either electron-rich olefins or serving as electrophilic dipolarophiles in 2 + 3 cycloadditions. The ultimate products in such cycloadditions are expected to be a consequence of rearrangements of the initially formed cycloadducts, and/or loss of sulfur dioxide (or sulfur monoxide) following the cycloaddition step, depending on the particular reaction conditions. The relative ease of the cycloaddition should provide some indication concerning the extent of the aromaticity in these systems2. 

It has long been known that a, / -unsaturated sulfones resemble a, /i-unsaturated ketones and aldehydes in undergoing addition reactions with nucleophilic reagents43. These reactions are initiated by nucleophilic attack at the carbon to the sulfone group ... 

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