Alkynyl sulfonate

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. 

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.

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. 

A general method of synthesis of l-hetera-4-telluracyclohexa-2,5-dienes 90 is founded in the nucleophilic addition of telluride anion to type 91 diacetylene derivatives. The telluride dianion is prepared in situ from the elements in liquid ammonia. The reaction was carried out with methanol or mixtures with DMSO and liquid ammonia as solvents, with the following diacetylenes di(l-alkynyl)sulfides (73RTC1326), I-alkynylethynyl sulfides (75RTCI63), di(l-alkynyl)sulfones (78RTC244), and di(l-alkynyl)phosphi-noxides (75RTC92). 

When y-CH bonds are present in the R group of the alkynyliodonium ion, cyclopentenyl sulfones predominate. For example, the treatment of 5-phenyl-1-pentynyl(phenyl)-iodonium tetrafluoroborate with te/ra- -butylammonium benzenesulfinate in THF (i.e. homogeneous conditions) affords a moderate yield of l-phenylsulfonyl-3-phenylcy-clopentene and a low yield of the corresponding alkynyl sulfone (equation 51)32. With appropriately constructed alkynyliodonium ions, annulated cyclopentenyl sulfones are obtained (equations 52 and 53)32. 

TABLE 4. Synthesis of alkynyl sulfones from alkynyl(phenyl)iodonium salts... 

The reactions of / -ketoethynyl- and ) -amidoethynyl(phenyl)iodonium triflates, 17 and 18, with sodium / -toluenesulfinate illustrate the synthetic potential of alkynyliodonium salts33. Although the direct attachment of a carbonyl group to the / -carbon atom of the triple bond in alkynyliodonium ions might be expected to facilitate alkynyl sulfone formation via the Ad-E mechanism, this mode of reactivity has not been observed. Instead, the MC pathway with carbenic insertion dominates and affords sulfones containing the... 

The trouble is that pyrrole will not do this reaction as it is so good at electrophilic substitution. What happens instead is that pyrrole acts as a nucleophile and attacks the electron-deficient alkene. The answer is to make pyrrole less nucleophil ic by acylating the nitrogen atom with the famous Boc protecting group (Chapter 24). We will see in the next section how this may be done. A good Diels-Alder reaction then occurs with a alkynyl sulfone. 

Selenosulfonate resin 44 has also been used in radical additions to alkynes in an approach to alkynyl sulfones (Scheme 11) [9]. Radical selenosulfonation... 

Addition of the selenolate that is prepared from diphenyl diselenide by reduction with NaBH4 to conjugate enyne sulfones 20 occurs at the d-position of the sulfonyl group to give 4-phenylseleno-l-sulfonylbuta-1,3-dienes 21 regio- and stereoselectively (Scheme 28) [50]. On the other hand, addition of PhSeNa to the conjugated alkynyl sulfone 22 that has a -phenylseleno substituent affords the anti-Michael adduct 23 preferentially (Scheme 29) [51]. 

In the analogous [3 + 2] cycloadditions of the more polarisable alkynyl sulfones, the trend in favour of forming the adduct (144), as compared with (145), is much more pronounced indeed, the product (144) is the sole adduct obtained in the majority of cases (Scheme 59). 

Trifluoromethanesulfonylalkynes (150) and activated alkynyl sulfones (151) both participate in [4+2] cycloaddition reactions with dienes under relatively mild conditions. For instance, with cyclopentad iene (146) and butadiene (152) they yield the adducts (153) and (154), respectively (Scheme 61). 

Suzuki, H., and Abe, H., A new straightforward synthesis of alkynyl sulfones via the sonochemical couphng between alkynyl halides and copper sulfinates. Tetrahedron Lett., 37, 3717, 1996. 

Alkynyl(phenyl)iodonium sulfonates are stable, microcrystalline substances that can be stored and used indefiniteiy with little or no decomposition. They have been employed in the formation of aryl (2-furyl)iodonium tosylates, alkynyl sulfonate, carboxylate and phosphate esters, tricoordinate vinyliodinane species,fO and alkylidenecarbene-iodonium ylides. <... 

A dramatic application was the asymmetric synthesis of epibatidine 70 by Simpkins.18 Diels-Alder reaction of the deactivated pyrrole 63 with the alkynyl sulfone 64 gave the bicyclic core 65 of epibatidine. Selective reduction gave the compound 66 needed for epibatidine, but in racemic form. A directed lithiation (chapter 7) and sulfonation led to achiral bis sulfone 67. 

Replacement of an unsaturated phenyliodo group. Formation of unsaturated sulfones by a tandem Michael addition-elimination is a highly efficient process that allows the synthesis of (Z)-l,2-bis(benzenesulfonyl)alkenes from (Z)-jS-(benzenesul-fonyl)alkenyliodonium salts. In S-ketoethynyl(phenyl)iodonium salts the electron-withdrawing power of the ketone group is weaker, the Michael addition is followed by carbene formation. Cyclopentenones are formed. A seemingly direct substitution of alkynyl(phenyl)iodonium salts gives alkynyl sulfones efficiently. ... 

An overview of the hydrozirconation of alkynyl sulfones reveals many variations in the regiochemistry. Starting from arylacetylenic sulfoxides, the hydrozirconation classically takes place in a cis fashion, with zirconium in the a-position... 

The reaction of alkoxide ions with alkynyliodonium salts is unproductive, leading to only decomposition products rather than the desired alkoxyacetylenes. Similarly, reaction of R3SiO does not lead to any siloxyalkynes. In contrast the softer sulfonate, carboxylate, and phosphate nucleophiles all readily react with alkynyliodonium salts leading to the corresponding alkynyl sulfonate, carboxylate and phosphate esters [4]. 

Reaction of alkynyliodonium sulfonates, 9, in dry acetonitrile in the presence of catalytic amounts of AgOTs or CuOTf leads to the formation of alkynyl sulfonates, 70, in reasonable yields [Eq. (30)] [18], In a similar manner bis(alkynyliodonium) tosylates, 36, give modest yields of bisalkynyl tosylates, 71, accompanied by some monotosylates, 72 [Eq. (31)] [41]. 

Interaction of alkynyliodonium compounds with arylsulfinate salts is particularly interesting. When the R group of the alkynyl moiety lacks a y-CH bond, alkynyl sulfones (89, 90) are formed in excellent isolated yields [70, 71] [Eqs. (45), (46)]. When y-CH bonds are available, the intermediate unsaturated carbene (Scheme 3-3) prefers insertion over rearrangement and hence cyclopentenyl sulfones, 91, predominate, although some alkynyl sulfone formation is also observed as illustrated in [Eq. (47)] [72]. 

Alkynyl sulfones. A straightforward preparation of these sulfones consists of the nochemical induction of coupling of 1 -iodoalkynes with copper sulfinates (tosylates, etc.) - THF. 

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