Dataset Information

Organophosphorus-Catalyzed Deoxygenation of Sulfonyl Chlorides: Electrophilic (Fluoroalkyl)sulfenylation by PIII /PV =O Redox Cycling.

ABSTRACT: A method for electrophilic sulfenylation by organophosphorus-catalyzed deoxygenative O-atom transfer from sulfonyl chlorides is reported. This C-S bond-forming reaction is catalyzed by a readily available small-ring phosphine (phosphetane) in conjunction with a hydrosilane terminal reductant to afford a general entry to sulfenyl electrophiles, including valuable trifluoromethyl, perfluoroalkyl, and heteroaryl derivatives that are otherwise difficult to access. Mechanistic investigations indicate that the twofold deoxygenation of the sulfonyl substrate proceeds by the intervention of an off-cycle resting state thiophosphonium ion. The catalytic method represents an operationally simple protocol using a stable phosphine oxide as a precatalyst and exhibits broad functional-group tolerance.

SUBMITTER: Ghosh A

PROVIDER: S-EPMC6388095 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Publications

Organophosphorus-Catalyzed Deoxygenation of Sulfonyl Chlorides: Electrophilic (Fluoroalkyl)sulfenylation by P<sup>III</sup> /P<sup>V</sup> =O Redox Cycling.

Ghosh Avipsa A Lecomte Morgan M Kim-Lee Shin-Ho SH Radosevich Alexander T AT

Angewandte Chemie (International ed. in English) 20190125 9

A method for electrophilic sulfenylation by organophosphorus-catalyzed deoxygenative O-atom transfer from sulfonyl chlorides is reported. This C-S bond-forming reaction is catalyzed by a readily available small-ring phosphine (phosphetane) in conjunction with a hydrosilane terminal reductant to afford a general entry to sulfenyl electrophiles, including valuable trifluoromethyl, perfluoroalkyl, and heteroaryl derivatives that are otherwise difficult to access. Mechanistic investigations indicate ...[more]

PMID: 30632657

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Project description:Experimental, spectroscopic, and computational studies are reported that provide an evidence-based mechanistic description of an intermolecular reductive C-N coupling of nitroarenes and arylboronic acids catalyzed by a redox-active main-group catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide, i.e., 1·[O]). The central observations include the following: (1) catalytic reduction of 1·[O] to PIII phosphetane 1 is kinetically fast under conditions of catalysis; (2) phosphetane 1 represents the catalytic resting state as observed by 31P NMR spectroscopy; (3) there are no long-lived nitroarene partial-reduction intermediates observable by 15N NMR spectroscopy; (4) the reaction is sensitive to solvent dielectric, performing best in moderately polar solvents (viz. cyclopentylmethyl ether); and (5) the reaction is largely insensitive with respect to common hydrosilane reductants. On the basis of the foregoing studies, new modified catalytic conditions are described that expand the reaction scope and provide for mild temperatures (T ? 60 °C), low catalyst loadings (?2 mol%), and innocuous terminal reductants (polymethylhydrosiloxane). DFT calculations define a two-stage deoxygenation sequence for the reductive C-N coupling. The initial deoxygenation involves a rate-determining step that consists of a (3+1) cheletropic addition between the nitroarene substrate and phosphetane 1; energy decomposition techniques highlight the biphilic character of the phosphetane in this step. Although kinetically invisible, the second deoxygenation stage is implicated as the critical C-N product-forming event, in which a postulated oxazaphosphirane intermediate is diverted from arylnitrene dissociation toward heterolytic ring opening with the arylboronic acid; the resulting dipolar intermediate evolves by antiperiplanar 1,2-migration of the organoboron residue to nitrogen, resulting in displacement of 1·[O] and formation of the target C-N coupling product upon in situ hydrolysis. The method thus described constitutes a mechanistically well-defined and operationally robust main-group complement to the current workhorse transition-metal-based methods for catalytic intermolecular C-N coupling.

Dataset Information

Organophosphorus-Catalyzed Deoxygenation of Sulfonyl Chlorides: Electrophilic (Fluoroalkyl)sulfenylation by PIII /PV =O Redox Cycling.

Publications

Organophosphorus-Catalyzed Deoxygenation of Sulfonyl Chlorides: Electrophilic (Fluoroalkyl)sulfenylation by P<sup>III</sup> /P<sup>V</sup> =O Redox Cycling.

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