Efficient synthesis of 4-vinyl α,β-unsaturated γ-lactams by ring-closing enyne metathesis reactions

Computational Chemistry-Assisted Highly Selective Radical Cascade Cyclization of 1,6-Enynes with Thiols: Access to Sulfur-Substituted 4-Enyl-2-Pyrrolidones

In this study, an efficient method for the synthesis of sulfur-substituted 4-enyl-2-pyrrolidones was successfully developed through AIBN-promoted highly selective 5-exo-dig radical cascade cyclization of 1,6-enynes with sulfur sources with the aid of theoretical and computational chemistry. This protocol enables the first practical and green synthesis of an array of 4-enyl-2-pyrrolidones in moderate-to-good yields with broad substrate scopes and high regioselectivities (>20:1). Moreover, excellent stereoselectivities have also been achieved (up to >20:1, Z/E). Most interestingly, when the sulfur source is electron-rich thiophenol, reverse stereoselectivities were discovered. In addition, the control experiments indicate that the cascade cyclization is realized by radical reactions, and the detailed reaction mechanism and regioselectivities have also been explained by theoretical studies.

Facile terminal functionalization of peptides by protease-catalyzed chemoenzymatic polymerization toward synthesis of polymeric architectures consisting of peptides

Terminal functionalized polypeptides were synthesized in one-pot chemoenzymatic polymerization using protease for constructing special polymeric architectures.

Divergent reaction pathways of homologous and isosteric propargyl amides in sequential Ru/Pd-catalyzed annulations for the synthesis of heterocycles

Cu-catalyzed three-component coupling of imines with benzoyl chloride and terminal arylalkynes followed by enyne ring-closing metathesis (RCM) and Heck cyclization afforded medicinally relevant benzoindolines, cyclopropane-fused indenopyridines, pyrroloquinolines, or 1,7-tetrahydrophenanthrolines via divergent cyclization pathways. Unexpectedly, the Pd-catalyzed cyclization of heterocyclic dienes proceeded via regiodivergent 5-exo or 6-endo pathways depending on the ring size (n = 1, 2) or the presence of isosteric groups (CH vs N). A one-pot protocol for the enyne-RCM/Heck annulation featuring a sequential addition of the Ru and Pd catalysts was developed maximizing the synthetic efficiency.

Synthesis of fused multicyclic compounds containing macrocycles by dienyne ring-closing metathesis and Diels-Alder reactions

Fused bicyclic compounds comprising small and large rings were synthesised by dienyne ring-closing metathesis (RCM) using Grubbs' catalyst. By taking advantage of faster small ring cyclisation compared with macrocyclisation, single isomers were obtained rather than mixtures of two isomers with different ring sizes. Using this process, various fused bicyclic compounds comprising small rings (5-7- membered) and large rings (14-17- membered) were obtained. By increasing reaction temperature and catalyst loading, the product conversion was improved in a predicted manner. This method produced E-olefins on the macrocycles with high selectivity. Also, the selectivity issues of tandem RCM for the synthesis of fused bicyclic compounds comprising small and medium rings were investigated. Lastly, the prepared bicyclic compounds with small and large rings contained 1, 3-dienes that underwent a further modification reaction, such as Diels-Alder, to produce more complex compounds. These Diels-Alder reactions produced tri- and tetracyclic compounds containing a macrocycle with single diastereomers, suggesting that the methodology demonstrated here could be a powerful tool for rapid preparation of highly complex molecules.