Highly Functionalized Pyridines Synthesis from N-Sulfonyl Ketimines and Alkynes Using the N–S Bond as an Internal Oxidant

Abstract

The N-S bond-based internal oxidant offers a distinct approach for the synthesis of highly functionalized pyridines. A novel Rh(III)-catalyzed one-pot process undergoes an efficient C-C/C-N bond formation along with desulfonylation under very mild conditions. The method is quite simple, general, and efficient.

Rh(iii)-catalyzed synthesis of tetracyclic isoquinolinium salts via C–H activation and [4+2] annulation of 1-phenyl-3,4-dihydroisoquinolines and alkynes in ethanol

“…It is noteworthy that the reaction could get almost quantitative yield in ethanol, with 99% yield in 4 h (entry 10). Meanwhile, we compared the effects of additives, such as copper salts, K 2 S 2 O 8 , C 6 H 5 I(O 2 CCH 3 ) 2 and 2,3-dicyano-5,6-dichlorobenzoquinone (DDQ) (entries [11][12][13][14][15][16]. Among these additives, Cu(OAc) 2 gave the best yield of 99% for 3aa in 10 minutes (entry 12).…”

Transition‐Metal‐Catalyzed C−H Functionalization for Construction of Quaternary Carbon Centers

“…NÀSb onds as oxidizing directing groups are rarely introduced in transition-metal-catalyzed CÀHf unctionalization, probablydue to the lower oxidizingpotential of a N-S bond. [135] Recently,L ia nd co-workers [136] disclosed ar hodium-catalyzed redox-neutral Scheme83. Rh-catalyzed asymmetric [4+ +1] annulation of benzamides with diazo compounds.…”

“…N−S bonds as oxidizing directing groups are rarely introduced in transition‐metal‐catalyzed C−H functionalization, probably due to the lower oxidizing potential of a N ‐S bond . Recently, Li and co‐workers disclosed a rhodium‐catalyzed redox‐neutral annulation of N ‐sulfinyl ketoimines with two molecules of acrylates for the formation of 1 H ‐isoindoles 292 bearing an N ‐substituted quaternary center, in which the cleavage of N ‐S bonds of N ‐sulfinyl ketoimines served as the oxidants (Scheme ).…”

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

“…Consequently, many contributions have been made by synthetic chemists to search for new method for the efficient synthesis and functionalization of pyridines. Among the most significant techniques are condensation reactions between reactive carbonyls and amines (namely Hantzsch [ 10 ] and Chichibabin pyridine synthesis [ 11 – 12 ]), transition metal salts-catalyzed [4 + 2] [ 13 – 18 ], [2 + 2 + 2] [ 19 – 26 ], and [3 + 3] cyclization reactions [ 27 ], multicomponent reactions [ 28 – 33 ], and direct C–H functionalizations on the pyridine rings [ 34 – 36 ]. Particularly, the fascinating construction of pyridines bearing a carboxylate or CN group at C3 position has been a lucrative target for chemists due to the pharmaceutically privileged status ( Fig.…”