Synthesis of six-membered oxygenated heterocycles through carbon–oxygen bond-forming reactions (original) (raw)
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Recent development in the transition metal-catalyzed cyclization reactions for organic syntheses in the author's laboratories is summarized, which includes (i) novel silylcarbocyclizations (SiCaCs) and carbonylative carbotricyclizations, (ii) intramolecular silylformylations and desymmerization of siloxydiynes by sequential double silylformylation, (iii) efficient total synthesis of (+)-prosopinine, (iv) enantioselective desymmetrization of aminodienes, and (iv) new and efficient routes to 1-azabicyclo[x.y.0]alkane amino acids. All these processes are catalyzed by Rh or RhCo complexes, and useful for rapid and efficient construction of a variety of heterocyclic and carbocyclic compounds. Mechanisms of these new carbocyclization and cyclohydrocarbonylation reactions are also discussed.
Advanced Synthesis & Catalysis, 2020
Synthesis of pharmaceutically active heterocycles is always appealing as the majority of the widely used drugs contain heterocyclic moieties as their core structure. So, the straightforward construction of heterocycles from readily available/accessible reagents is one of the prime targets of the synthetic chemists. In this context, C-H functionalization has emerged as an effective tool for the designing and synthesis of various heterocyclic moieties as it offers a straightforward and step-economic pathway. On the other hand, the readily available/accessible conjugated carbonyls are well-known reagents for the construction of carbocycles and heterocycles over the years. However, the employment of C-H functionalization of the two C-H bonds of the conjugated alkene in carbocycle/heterocycle synthesis was not so explored. In the last decade, much focus has been paid on the synthesis of various pharmaceutically active heterocycles through C-H bond functionalization of α,βunsaturated aldehydes/ketones. These protocols have been developed through either oxidative coupling of conjugated carbonyls with suitable coupling partners or intramolecular C-H bond functionalization of conjugated carbonyls. In this review, we will discuss all the methodologies developed for the synthesis of heterocycles employing intermolecular C-H bond functionalization of conjugated carbonyls. The mechanistic pathways and usefulness of the methodologies will be also highlighted.
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The so-called ''enabling techniques'' can dramatically promote the synthesis of N-heterocycles. Besides facilitating very quick cyclization, these technologies bring with them process intensification, safer protocols, cost reduction, energy savings, and waste minimization. We herein describe a series of efficient N-heterocycle cyclizations carried out under microwave and/or ultrasound irradiation.
Synthesis of Heterocycles via Radical-Polar Crossover Cycloadditions
2014
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Angewandte Chemie International Edition, 2012
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2017
During the course of this PhD, a new one-pot thermal Overman rearrangement and ring-closing metathesis process was developed for the preparation of polycyclic compounds. In this method, commercially available phenols and anilines were converted to alkene derived allylic alcohols and then transformed via a one-pot process into 5-amino 2,5-dihydro-1-benzoxepines and 5-amino 2,5-dihydro-1H-benzazepines. The synthetic utility of these compounds was explored with the preparation of highly substituted hydroxylated analogues as well as a highly active hypotensive agent. A novel one-pot process was also developed for the synthesis of allylic amide derived 2H-chromenes. The key substrates, propargyloxy cinnamyl alcohols were rapidly prepared from readily available salicylaldehydes. One-pot thermal Overman rearrangement of the corresponding allylic trichloroacetimidates, followed by a gold(I)-catalysed hydroarylation gave the 2H-chromenes in high yields. A mild chemoselective method for the o...