Additions of Organocopper Reagents and Heteroatom Nucleophiles to 1-Phenylseleno-2-(p-toluenesulfonyl)ethyne. Preparation of Vinyl and Allenic Sulfones and Formation of Michael, Anti-Michael, and Rearrangement Products

Abstract

1-Phenylseleno-2-(p-toluenesulfonyl)ethyne (4) was produced nearly quantitatively from p-(toluenesulfonyl)ethyne and benzeneselenenyl chloride. It underwent stereo-and regioselective synadditions of organocopper reagents RCu(CN)Li to the -position of the sulfone moiety to afford adducts 5. Further reaction of the products with reagents RCu(SePh)Li resulted in substitution of the phenylseleno group with retention of configuration. Control of E,Z-stereochemistry in the product , -disubstituted vinyl sulfones is therefore achieved by the order of addition of the reagents. Selenoxide syn-elimination of adducts 5 afforded the corresponding allenic sulfones. The additions of amines and alkoxides to 4 produced the corresponding anti-Michael regioisomers (where attack occurred R to the sulfone group) as the major or sole products. The additions were highly stereoselective, proceeding by anti-addition in the anti-Michael series and by syn-addition in the corresponding Michael regioisomers. The reactions of 4 with thiolates and selenolates were more complex, affording rearranged adducts and Michael adducts as the major and minor products, respectively. The formation of the rearranged products can be rationalized by a series of additionelimination processes. Phenylselenoethyne (43) underwent conjugate additions of pyrrolidine, sodium methoxide, sodium ethanethiolate, and benzeneselenolate anion, affording the corresponding cis isomers via anti-addition. The experiments with heteroatom nucleophiles and acetylenes 4 and 43 show that the phenylseleno group has a surprisingly large activating effect upon conjugate additions.Unsaturated sulfones have numerous uses in organic synthesis. 1 The sulfone group, like the carbonyl group, has an activating effect upon an adjacent carbon-carbon double or triple bond with respect to conjugate additions and cycloadditions. The resulting products are saturated or vinyl sulfones that can be further elaborated via reactions of the corresponding sulfone-stabilized R-carbanions with electrophiles. Furthermore, subsequent reductive desulfonylation permits the sulfone moiety to act as a temporary activating group. Thus, for example, acetylenic sulfones function as the synthetic equivalents of dipoles and "multipoles", such as 1 and 2 in Scheme 1.In principle, further opportunities for synthetic transformations that can be used in conjunction with the above become possible if an appropriate nucleofuge is installed at the -position of an acetylenic sulfone. This provides the site for the introduction of an additional nucleophile by substitution of the nucleofuge (Scheme 1) or for the regeneration of unsaturation by its elimination. It appeared to us that the phenylseleno group might be an appropriate -substituent for this purpose, since certain -selenovinyl sulfones are known to undergo substitution reactions of the selenium moiety with organocuprates 2 and other nucleophiles, 3,4 as well as syn-elimination reactions of their corresponding selenoxides. 5,6 We now report the preparation of the novel...

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

“…These results were explained by assuming the association of the metal to the sulfonyl oxygen (as has been described previously28d,45,46) in a step prior to the α‐attack of the alkoxides on the sulfonylacetylenes (Scheme ). This would explain the failure of the reactions in the presence of 18‐crown ether.…”

“…The strongly electron‐withdrawing character of the sulfonyl group makes it able to stabilize α‐sulfonyl carbanions, thus being responsible for a large variety of conjugated additions C‐β,28a and to activate multiple bonds for different cycloaddition reactions 28b. These could be considered the results of the normal and expected polarization of the triple bond in a sulfonyl acetylene, as occurs with organocuprates28c,28d (Scheme , top). However, the addition of some organometallics to these compounds can occur at C‐α, according to an unexpected initial anti ‐Michael process (Scheme , bottom).…”

Click Chemistry in Materials Science

“…[ 24,25 ] Moreover, the synthetic accessibility of these aryl-functionalized cyclooctynes makes them particularly attractive for catalyst-free cycloaddition reactions with azides. [ 22,26 ] Simple electron-defi cient alkynyl groups, such as alkynyl esters, [ 27 ] amides, [ 28 ] and sulfones, [ 29 ] have also been employed to effect catalyst-free azide-alkyne cycloaddition; however, the rapid addition reaction of amines to sulfonyl alkynes [ 30 ] suggests that the reaction orthogonality of these systems may be compromised.…”

The synthesis of thiols, selenols, sulfides, selenides, sulfoxides, selenoxides, sulfones and selenones

“…The addition of organocopper reagents to 1-phenylseleno-2-( ptolylsulfonyl)ethyne 77 gives (Z)-β-(phenylseleno)vinyl sulfones in good yield. 327 Further treatment of these adducts with reagents of the form RCu(SePh)Li, results in displacement of the phenylseleno group with retention of configuration. Thus, by varying the order of reagent addition, a variety of β,βdisubstituted vinyl sulfones can be prepared stereoselectively (Scheme 174).…”