Triflic acid-promoted aza-Prins-Ritter reaction sequence: a novel synthesis of 4-amidopiperidine derivatives

Sequential Photochemical and Prins Reactions for the Diastereoselective Synthesis of Tricyclic Scaffolds

“…Initial investigations were based on tandem Prins–Ritter reaction conditions first reported by Willis and co‐workers for the synthesis of 4‐amidotetrahydropyrans . Yadav and co‐workers have used similar conditions for the formation of 4‐amidopiperidine derivatives, and a Sakurai–Prins–Ritter reaction to prepare 2,6‐disubstituted tetrahydropyrans has also been developed . Thus 1 was treated with benzaldehyde and trifluoromethanesulfonic (triflic) acid in acetonitrile at room temperature.…”

Sequential Photochemical and Prins Reactions for the Diastereoselective Synthesis of Tricyclic Scaffolds

“…Initial investigations were based on tandem Prins−Ritter reaction conditions first reported by Willis et al for the synthesis of 4-amidotetrahydropyrans. [14] Yadav et al have used similar conditions for the formation of 4-amidopiperidine derivatives [15] and a Sakurai−Prins−Ritter reaction to prepare 2,6-disubstituted tetrahydropyrans has also been developed. [16][17][18] Thus, 1 was treated with benzaldehyde and triflic acid (TfOH) in acetonitrile at room temperature.…”

Recent developments in Ritter reaction

“…Piperidine derivatives are one of the most promising therapeutic agents for a wide variety of diseases. In 2011, Reddy et al 34 introduced a novel procedure for the synthesis of 4-amidopiperidine derivatives via an aza-Prins-Ritter reaction sequence using triic acid (TfOH, 120 mol%) as a catalyst in acetonitrile under mild conditions (Scheme 30). A large range of aromatic aldehydes and aliphatic aldehydes underwent smooth coupling with N-tosylhomoallylic amine in acetonitrile to give the corresponding products of 4-amidopiperidine derivatives with trans-selectivity in good yields.…”

“…Many useful compounds have been synthesized through Ritter or Ritter-type reaction, including asymmetrical di-and tri-substituted ureas, 3-substituted-3amino-oxindoles, 4-acyl-aminotetrahydroindazoles, N-(4-iodo-1,3-diarylbutyl) acetamides, 4-amidopiperidine derivatives and aza-bicyclic alkaloids. [4][5][6][7][8]10,11,[13][14][15][16][17][19][20][21][22][23][24]27,[30][31][32][33][34][35][36] This review focuses on new ndings in Ritter or Ritter-type reaction in the last four years and provides a concise overview of recent progress in this area.…”