Versatile Synthesis of Functionalized Tetrahydroisoquinolines by Ring Transformation of 2H-Pyran-2-ones

Abstract

Functionalized tetrahydroisoquinolines are convenient precursors for the construction of numerous heterocyclic compounds of therapeutic importance. In this paper we have illustrated an efficient synthesis of highly substituted tetrahydroisoquinolines from 2H-pyran-2-ones via nucleophile-mediated ring transformation with tert-butyl-4-oxopiperidine-1-carboxylate followed by acid-mediated cleavage of the tert-butyloxycarbonyl group. The products were achieved smoothly in high yields with flexibility of various substituents.

Metal‐Free Synthesis of Thermally Stable Fluorescent p‐Terphenyls by Ring Transformation of 2H‐Pyran‐2‐ones

“…In our earlier research studies, 2H-pyran-2-ones have been proved as versatile substrates to achieve the synthesis of various scaffolds such as m-teraryls, [43] polycyclic compounds, [44,45] and pyridines [46,47] and diarylmethanes. [48] 2Hpyran-2-ones can react with nucleophiles as they are having three electrophilic centres C-2, C-4, C-6.…”

“…On the basis of our previous studies, [43][44][45] In order to explore the applicability of 2H-pyran-2-ones 4, the same substrates 5 were treated with cyclohexanone 8 under similar reaction conditions and functionalized cyclic terphenyls 9 were isolated in high yields (Table 4, entries 1-4). Various cyclic and acyclic amino groups at C-4 position in substrates 5 were successfully tolerated during these ring transformation reactions.…”

“…On the basis of our previous studies, the possible mechanistic pathway for the synthesis of functionalized p ‐terphenyls 7 by the ring transformation reaction of 6‐([1,1′‐biphenyl]‐4‐yl)‐4‐amino‐2 H ‐pyran‐2‐ones 5 and malononitrile 6 is depicted in Scheme . Initially, the formation of carbanion occurs from malononitrile 6 in the presence of base.…”

Transition-metal-free synthesis and photophysical studies of highly functionalized (E)-stilbenes

“…The well-known methods to synthesize stilbene derivatives include transition metal couplings, such as Sonogashira, Mizoroki-Heck, Negishi, Suzuki-Miyaura, Stille, Grubbs & McMurry, Knoevenagel-Doebner, Wittig, or Horner-Wadsworth-Emmons (HWE) olefination, Ramberg-Bucklund reactions, and Perkin aldol condensation. [36][37][38] In the course of our continuous investigation into substituted aromatic systems involving donors and acceptors, [39][40][41][42][43][44][45][46] we have devised an efficient approach to craft donor-acceptor p-conjugated (D-p-A) stilbenes. In this molecule, the secondary amine at the C4 position acts as the donor group and the CN group acts as the acceptor functionality.…”

“…In the course of our continuous investigation into substituted aromatic systems involving donors and acceptors, 39–46 we have devised an efficient approach to craft donor–acceptor π-conjugated (D–π–A) stilbenes. In this molecule, the secondary amine at the C4 position acts as the donor group and the CN group acts as the acceptor functionality.…”