Sulfones alkynyl

Under similar conditions (diethyl ether or THF as solvent) the reaction of lithium alkynylides with methanesulfonyl chloride (CH35O2CI) gave the corresponding alkynyl sulfones in low to moderate yields. 

Alkynyl trifluoromethyl sulfones add dimethylformamide and dimethylsul-foxide to give products in good yields The consistent stereospeciticity of the reaction syn addition product only) suggests that an unstable [2+2] cycloaddition intermediate is initially formed [J4] (equation 12). 

Bis(alkynyl)-l//-pyrazoles are also obtained by the same procedure. The reaction of (Z)-enediyne sulfones with diazomethane gives bis(alkynyl)-3//-... 

McDowell and Stirling194 studied electronic effects upon the reactivity of aryl vinyl sulfones towards amines. Rate constants for t-butylamine addition in ethanol at 25 °C were well correlated by the Hammett equation, with p = 1.59. Comparison of this with p values for H-D exchange mentioned above191 suggested considerable carbanionic character in the transition state, perhaps in a concerted mechanism. Rates of addition of amines to alkenyl, allenyl and alkynyl p-tolyl sulfones have also been measured195. 

For trisubstituted olefins, the nucleophile attacks predominantly at the less substituted end of the allyl moiety, e.g. to afford a 78 22 mixture of 13 and 14 (equation 7). Both the oxidative addition of palladium(O) and the subsequent nucleophilic attack occur with inversion of configuration to give the product of net retention7. The synthesis of the sex pheromone 15 of the Monarch butterfly has been accomplished by using bis[bis(l,2-diphenylphosphinoethane)]palladium as a catalyst as outlined in equation 87. A substitution of an allyl sulfone 16 by a stabilized carbon nucleophile, such as an alkynyl or vinyl system, proceeds regioselectively in the presence of a Lewis acid (equation 9)8. The... 

TABLE 4. Cross-coupling reaction of alkynyl sulfones ArS02C=CR with lithium reagents R Li ... 

Scheme 4.7. Variations in the regiochemistry of the hydrozirconation of alkynyl sulfones.

Recently, Hiroi and co-workers reported a palladium-catalyzed asymmetric transformation of chiral 2-alkynyl sulfmates 142 into allenyl sulfones 145 (Scheme 4.38) [58], Treatment of 142 with Pd(OAc)2 in the presence of a phosphine ligand afforded allenylsulfones 145 with high stereospecificities (73-89%) in good yields, probably through intermediates 143 and 144. 

Copper iodide acts as an efficient reagent for the nucleophilic displacement of 1-haloalkynes. It transforms 1-bromoalkynes (72) into 1-iodoalkynes (73) which, on further treatment with copper(II) bis(arenesulfinate), are converted into the corresponding alkynyl aryl sulfones (74). An electron transfer between 1-haloalkynes and copper(I) salts is believed to take place for the copper-assisted halogen-exchange reaction at the acetylenic carbon atom. 

Conjugate addition of methylamine to vinyl alkynyl sulfoxides and sulfones also led to formation of 1,4-thiazine 1-oxides and 1,1-dioxides (Equation 74) <1979S47>. 

Di(l-alkynyl)sulfides are formed in excellent yields, if (freshly distilled) sulfur dichloride is added to a solution or suspension of a lithium alkynylide in Et20 [106). In an analogous manner, di(l-alkynyl)sulfoxides are formed from thionyl chloride and an alkynyllithium [106], while sulfinyl chlorides R S(=0)G may be used to prepare the sulfoxides RC=CS(=0)R Preliminary experiments suggest that interaction between alkynyllithium and sulfonyl chlorides R S02C1 can give both sulfones ROCSOjR and chlofo-alkynes RCsCCl [2). 

When the phenyl-substituted alkynyl sulfone 42 is used as a substrate for the Cu-catalyzed carbomagnesiation, interesting nucleophile-dependent stereoselectivity is observed. While the use of allyl Grignard reagent results in a syn addition, the use of aryl Grignard reagent results in an awh -carbomagnesiation (Scheme 25). ... 

Bromination of the enol ether product with two equivalents of bromine followed by dehydrobromination afforded the Z-bromoenol ether (Eq. 79) which could be converted to the zinc reagent and cross-coupled with aryl halides [242]. Dehydrobromination in the presence of thiophenol followed by bromination/dehydrobromination affords an enol thioether [243]. Oxidation to the sulfone, followed by exposure to triethylamine in ether, resulted in dehydrobromination to the unstable alkynyl sulfone which could be trapped with dienes in situ. Alternatively, dehydrobromination of the sulfide in the presence of allylic alcohols results in the formation of allyl vinyl ethers which undergo Claisen rearrangements [244]. Further oxidation followed by sulfoxide elimination results in highly unsaturated trifluoromethyl ketonic products (Eq. 80). 

Grignard reagents convert aromatic sulfonyl chlorides or aromatic sulfonates to sulfones. Aromatic sulfonates have also been converted to sulfones with organolithium compounds.1745 Vinylic and allylic sulfones have been prepared by treatment of sulfonyl chlorides with a vinylic or allylic stannane and a palladium-complex catalyst.1746 Alkynyl sulfones can be prepared by treatment of sulfonyl chlorides with trimethylsilylalkynes, with an AICL catalyst.1747... 

An intramolecular Diels-Alder reaction of an alkynyl sulfone was used [537] in the synthesis of a ring fragment of vitamin D3. 

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