Silver-Catalyzed Intermolecular Hydroamination of Alkenes and 1,3-Dienes

Abstract

Silver triflate is used as efficient catalyst for the intermolecular addition of 4-toluenesulfonamide to alkenes under thermal or microwave heating. The hydroamination of 1,3-dienes can be performed at 85 ˚C with low catalyst loading (0.1-5 mol%) or at room temperature using 1 mol% of AgOTf, the use of HOTf affording similar results.

alkenes - conjugated dienes - hydroamination - sulfon­amides - silver catalysts

References and Notes

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General Procedure for the Hydroamination of Alkenes and Dienes
To a mixture of silver salt (see Tables  [¹] and  [²] ) and sulfonamide (171 mg, 1 mmol) in dry solvent (2 mL, see Tables  [¹] and  [²] ) was added the alkene or 1,3-diene (4 mmol) with magnetic stirring in a sealed tube under argon atmosphere in the dark. For neat experiments (see Table  [²] , entries 6-8) no solvent was added. After the corresponding reaction time under the conditions indicated in Tables  [¹] and  [²] (for microwave heating the vessel was sealed with a pressure lock, and the mixture was heated at 90 ˚C in a CEM Discover MW reactor at 70 W, 0.69 bar with air stream cooling during 30 min), to the reaction mixture cooled at r.t. was added H₂O (2 mL) and brine (2 drops). The organic layer was separated, and the aqueous phase was extracted with EtOAc (2 × 10 mL). All organic phases were mixed, dried with MgSO₄, and evaporated. Pure products were obtained by recrystallization or by flash chromatography.

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Crystallographic data (excluding structure factors) have been deposited with the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk./data_request/cif as supplementary publication no. CCDC 748465 [unit cell parameters: a 12.2371 (16), b 17.627 (2), c 7.9272 (11),
β 105.117 (3), space group P21/c].