Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

Abstract

Heterocyclic compounds are important organic compounds and have emerged as key scaffolds in numerous drugs, natural products, vitamins, biologically and pharmaceutically active compounds. Over the past few decades, the development of versatile methodologies employing propargylic alcohols as synthons for the construction of heterocyclic skeletons has attracted great attention from synthetic chemists. In this review, recent developments in the cascade cyclization of propargylic alcohols with diverse nucleophiles to construct heterocyclic compounds are summarized. According to the types of nucleophiles, these reactions can be divided into four categories: 1) Reactions involving C‐nucleophiles to capture allenyl carbocation; 2) Reactions involving O, S‐nucleophiles to capture allenyl carbocation; 3) Reactions involving N, P‐nucleophiles to capture allenyl carbocation; 4) Reactions involving halo‐nucleophiles to capture allenyl carbocation.

Relay Rhodium(I)/Acid Catalysis for Rapid Access to Benzo‐2H‐Pyrans and Benzofurans

“…[12] In an attempt to further explore the arylation of tertpropargyl alcohol 1 a with ortho-hydroxylated phenylboronic acid 2 a, an unprecedented hydroarylation product was exclusively generated (Scheme 2). [13] We envisioned combining this rhodium(I)-catalyzed arylation process with acid-catalyzed intramolecular cycli-zation would enable rapid generation of valuable benzo-fused oxacycles, [14,15] thus the relay rhodium(I)/ acid catalysis was investigated. To our delight, addition of strong Brønsted acid into the reaction system did not inhibit the reaction, and benzo-2H-pyran 4 a was obtained in good yield with p-toluenesulfonic acid as the co-catalyst.…”

Recent approaches for the synthesis of pyridines and (iso)quinolines using propargylic Alcohols

“…In recent years, many review articles have appeared describing the general reactivity of propargylic alcohols for the construction of various cyclic systems, including heterocyles. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] To the best of our knowledge, no focused reviews have appeared on the synthesis of six-membered nitrogen basedheterocyclic compounds by employing the propargylic alcohols as one of the key reactants. Thus, in this review article, we aimed to summarize various approaches to N-heterocyclic compounds from propargylic alcohols, and we have limited our focus to the pyridines, quinolines, and isoquinolines.…”

Transition Metal‐Catalyzed Hydroalkoxylation of Alkynes: An Overview

“…Transition-metal-catalyzed activation of alkynes has been studied extensively. [10] The intermolecular trapping of metal/ acid-activated alkynes with oxygen nucleophiles (alcohols) has been used widely for the generation of enol ether. In case of terminal alkynes, the alcohol traps the activated alkynes at the more substituted carbon due to the stability of vinyl carbocation i. e. path-A over path-B is preferred.…”