Unsaturated sulfones reaction with

Some additional examples, where the stereochemical outcome of the cycloaddition to chiral alkenes has been explained in terms of the Houk-Jager model, should also be mentioned. The diastereomer ratio found in the reaction of y-oxy-a,p-unsaturated sulfones (166), with Morita-Baylis-Hillman adducts [i.e., a-(a -hydro-xyalkyl)-acrylates (167)] (Scheme 6.27), with dispiroketal-protected 3-butene-1,2-diol (168), and with a,P-unsaturated carbonyl sugar and sugar nitroolefin (169) derivatives, all agree well with this model. 

The synthesis of electron-deficient diene 285 was achieved by the Stille coupling of P-trifluoromethanesulfonyl-a,P-unsaturated sulfone (284) with a 3-stannyl-a,P-unsaturated ester (283) (Scheme 74).148 Similarly, the preparation of a diverse range of enantiomerically pure 1- and 2-sulfinyl dienes has been achieved via Stille coupling of halovinyl sulfoxides and vinyl stannanes.149,150 Enantiomerically pure 1- and 2-sulfinyl dienes have been used extensively in asymmetric Diels-Alder reactions.111... 

Reaction [ 134] of a,/l-unsaturated aldehyde 309 (Scheme 100) and p,y-unsaturated sulfone 310 with the use of KHMDS as the base provided triene 311 the Z-isomer predominated, EjZ 18/82. When NaHMDS was used, the olefination product was obtained in 79% yield EjZ 56/44). 

Table 33 Reaction of f ,y-unsaturated sulfone 332 with aldehydes, according to...

Unexpected annulation occurred in an attempted Heck reaction of the a,f-unsaturated sulfone 157 with an excess of iodobenzene to give 158 in high yield. The use of Ag2C03 as a base is important [39]. The expected Heck product 159... 

The reaction of the enamines of cyclohexanones with a,ft-unsaluraled sulfones gives mixtures resulting from attack of the enamine at the a- and /(-carbons of the oc,/ -unsaturated sulfone. The ratio of x- and /1-adducts is dependent upon the reaction solvent, the geometry and structure of the sulfone1 4. The diastereoselectivity of these reactions is also poor. The reaction of lithium enolates of cyclic ketones with ( )-[2-(methylsulfonyl)ethenyl]benzene, however, gives bicyclic alcohols, as single diastereomers, that result from initial -attack on the oc,/ -unsaturated sulfone5. 

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 ... 

When a mixture of p-anisaldehyde and dimethyl sulfone was treated with excess potassium t-butoxide in DMF at 60-65 °C, bis-unsaturated sulfone 277 was obtained. In the reaction at 50 °C using a small amount of base, the main product was a heterocyclic compound, i.e., 2,4-di-p-methoxyphenyl-l,4-oxathiane 4,4-dioxide 278358. 

This chapter deals with (1) the transformation of the sulfone functionality into other functional groups by nucleophilic substitution reaction, and (2) the addition and elimination reaction of a,/i-unsaturated sulfones. Particular attention will be paid to recent uses of sulfones in organic syntheses1. 

Reaction of a-isocyano-a, / -unsaturated sulfones with primary aliphatic amines affords 1,5-disubstituted imidazoles 59 (equation 56)48. The reaction of aromatic amines such as aniline is too slow to be of practical use. Results of the preparation of 59 are listed in Table 5. 

Addition of amines to a,/J-unsaturated sulfones has been used in synthesis of key intermediates of biotin. In this reaction, benzylamine serves first as a base in the reaction with 60 to afford thiophene 1,1-dioxide (61) and also as a nucleophile to introduce two amino groups (equation 57)49. 

Reaction 31 appears to be little affected by substituent electronic effects or by steric effects of either sulfonyl chloride or styrenes. Treatment of /5-chlorosulfones with triethylamine in benzene affords the corresponding a, /5-unsaturated sulfones in excellent yield. The copper-catalyzed addition of sulfonyl iodides to simple and cyclic alkenes has also been exploited76. 

Arenesulfonyl chlorides77 as well as alkenesulfonyl chlorides78 react with vinylarenes in the presence of RuCl2(PPh3)3 and 1 molar equiv. of Et3N to form a,/ -unsaturated sulfones in 70-90% yields. The reaction mechanism for the ruthenium(II) catalyzed reaction involves a free-radical redox-transfer chain process as outlined below77 ... 

Nucleophilic addition to a, -unsaturated sulfones has long been known. For example, treatment of divinyl sulfone with sodium hydroxide has been known to afford bis( -hydroxyethyl) sulfone "", while the reaction of a- and -naphthyl allyl sulfones and allyl benzyl sulfone " with alkali hydroxide or alkoxide gave -hydroxy or alkoxy derivatives. In the latter reaction, the allyl group underwent prototropy to the 1-propenyl group, which in a subsequent step underwent nucleophilic attack . Amines, alcohols and sulfides are known to add readily to a, -unsaturated sulfones, and these addition reactions have been studied widely. In this section, the addition of carbon nucleophiles to a, ji-unsaturated sulfones and the reactions of the resulting a-sulfonyl carbanions will be examined. 

In addition to these physical studies at the Bureau, Tipson was able to return to his synthetic interests, both alone and in collaboration with other staff members. He was especially pleased to prepare D-talose in crystalline form, an accomplishment that had eluded Emil Fischer. Pursuing his longstanding interest in the reaction of sulfonic esters with iodide and following an earlier observation that the tetratosyl ester of erythritol is converted into butadiene by the action of sodium iodide and zinc, he demonstrated (with A. Cohen) that nonterminal unsaturation may be conveniently introduced into alditol derivatives by reaction of contiguous secondary sulfonates with sodium iodide and zinc dust in boiling A.A-dimethylformamide. This Tipson-Cohen reaction subsequently proved of great utility in other hands for the conversion of more complex carbohydrate structures into vicinal dideoxy derivatives. 

Silylcuprates have been reported to undergo reactions with a number of miscellaneous Michael acceptors [65]. Conjugate addition to 3-carbomethoxy acyl pyri-dinium salts [65a] affords 4-silyl-l,4-dihydropyridines. Oxidation with p-chlorand generates a 4-acyl pyridinium salt that gives the 4-silylnicotinate upon quenching with water, and methyl 4-silyl-2-substituted dihydronicotinates upon quenching with nucleophiles (nucleophilic addition at the 6-position). The stabilized anion formed by conjugate addition to an a, j8-unsaturated sulfone could be trapped intramolecularly by an alkyl chloride [65b]. 

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