Synthesis of PO(OR)2- and PR3+-Disubstituted Pyridines via N-(Trifluoromethylsulfonyl)pyridinium Triflates

Mirko Haase; Helmar Goerls; Ernst Anders

doi:10.1055/s-1998-2012

Synthesis 1998; 1998(2): 195-200
DOI: 10.1055/s-1998-2012

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Synthesis of PO(OR)₂- and PR₃ ⁺-Disubstituted Pyridines via N-(Trifluoromethylsulfonyl)pyridinium Triflates

Mirko Haase^* , Helmar Goerls, Ernst Anders

^*Institut für Organische Chemie und Makromolekulare Chemie der Universität Jena, Humboldtstraße 10, D-07743 Jena, Germany; Fax + 49(36 41)94 82 12; E-mail: c5eran@rz.uni-jena.de

Abstract

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The efficient synthesis of dialkoxyphosphoryl- and phosphonio-substituted pyridines is reported. The cationic heterocycle of N-(trifluoromethylsulfonyl)pyridinium triflate (3), or of analogous N-(trifluoromethylsulfonyl) compounds prepared from pyridine-4-phosphonium salts 5, turns out to be sufficiently activated to allow attack of P(OR)₃ and PR₃ nucleophiles to give the novel compounds bis(dialkoxyphosphoryl)pyridines 11 and phosphonio(dialkoxyphosphoryl)pyridines 13. For example, 13 a - d, with PO(OR)₂ at the C2 and PR₃ ⁺ at the C4 position, represent the first examples of an N-heteroaromatic ring substituted by both dialkoxyphosphoryl and phosphonio moieties. The structure of 13 b [PPh₃ ⁺/PO(O-i-Pr)₂] was confirmed by X-ray analysis. In most cases, the intermediate 1-(trifluoromethylsulfonyl)dihydropyridines, such as 7, 8 (monosubstituted) or 10 a and b and 12 a - d (disubstituted), are sufficiently stable for isolation.

N-(trifluoromethylsulfonyl)pyridinium triflates - regioselective nucleophilic substitution - C2- and C4-disubstituted pyridines - phosphites - phosphonium triflates

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Synthesis of PO(OR)2- and PR3 +-Disubstituted Pyridines via N-(Trifluoromethylsulfonyl)pyridinium Triflates

Synthesis of PO(OR)₂- and PR₃ ⁺-Disubstituted Pyridines via N-(Trifluoromethylsulfonyl)pyridinium Triflates