Enantioselective Synthesis of Multifunctionalized 4<i>H</i>-Pyrans via Formal [4 + 2] Annulation Process by Bifunctional Phosphonium Salt Catalysis
作者:Jia-Hong Wu、Jianke Pan、Juan Du、Xiaoxia Wang、Xuemei Wang、Chunhui Jiang、Tianli Wang
DOI:10.1021/acs.orglett.9b04079
日期:2020.1.17
highly enantioselective formal [4 + 2] annulation involving electron-deficient allenes as C2-synthons has been developed under bifunctional phosphonium salt catalysis. With this catalytic protocol, a wide range of synthetically interesting and highly functionalized chiral 4H-pyran derivatives were readily prepared in good yields (up to 99%) with outstanding diastereo- and enantioselectivities (up to
A Ba/Pd cooperative catalysis system was developed to enable the dehydrative cross-coupling of allylic alcohols with P-ylides to occur directly and promote a subsequent Wittigreaction in one pot. A variety of multisubstituted 1,4-dienes were isolated in good to excellent yields with broad P-ylides (stabilized by both ester and ketone carbonyl groups) and aldehyde (aliphatic and aromatic) substrates
Applications of Thermal Activation, Ball-milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides
作者:Żaneta A. Ignatiuk、Mikołaj J. Janicki、Robert W. Góra、Krzysztof Konieczny、Rafał Kowalczyk
DOI:10.1002/adsc.201801498
日期:2019.3.5
to conjugated en‐ynones was performed through the application of chiral squaramides. Three non‐classical approaches to promote the addition reaction were tested, including activation of the nucleophile by inorganic base in a biphasic aqueous system, thermal activation, and ball‐milling. Hydrogen‐bonding catalysis was effective in all these methods, providing 1,4‐addition products in high yields and
Phosphine-catalyzed [3+2] annulation of β-sulfonamido-substituted enones and sulfamate-derived cyclic imines has been developed, giving a series of imidazoline derivatives in moderate to excellent yields with good to excellent diastereoselectivities. A scale-up reaction worked well under mild reaction conditions. A possible mechanism was proposed on the basis of the results obtained.
Beyond the Corey–Chaykovsky Reaction: Synthesis of Unusual Cyclopropanoids via Desymmetrization and Thereof
作者:Kaushalendra Patel、Uttam K. Mishra、Dipto Mukhopadhyay、S. S. V. Ramasastry
DOI:10.1002/asia.201901108
日期:2019.12.13
Desymmetrization-based protocols for the synthesis of highly functionalized indeno-spirocyclopropanes and cyclopropa-fused indanes have been established through unexpected reactions triggered by the Corey-Chaykovsky reagent. These structures were further elaborated in one step to privileged scaffolds such as fluorenones, indenones, and naphthaphenones. For instance, an acid-catalyzed transformation