An efficient enantioselectiveorganocatalytic method for the synthesis of N-alkylated indoles with α-branched alkyl substituents from the corresponding unsaturated indolyl ketones via a Michaeladdition has been developed. The resulting products were obtained in high enantioselectivities and in good yields. Various nucleophiles (nitroalkanes, malononitrile, malonic esters) can be used. The substitution
A mild and facile Peterson olefination has been developed employing low catalyst loading of the Brønstedacid HNTf2. The reactions are typically performed at room temperature, with the reaction tolerant to a range of useful functionalities. Furthermore, we have extended this methodology to the synthesis of enynes.
Enantioselective Inverse Electron Demand (3 + 2) Cycloaddition of Palladium-Oxyallyl Enabled by a Hydrogen-Bond-Donating Ligand
作者:Yin Zheng、Tianzhu Qin、Weiwei Zi
DOI:10.1021/jacs.0c11504
日期:2021.1.20
Cycloaddition reactions between oxyallylcations and alkenes are important transformations for the construction of ring systems. Although (4 + 3) cycloaddition reactions of oxyallylcations are well-developed, (3 + 2) cycloadditions remain rare, and an asymmetric version has not yet been developed. Moreover, because oxyallylcations are highly electrophilic, only electron-rich olefins can be used as
β-Silyl-Assisted Tandem Diels–Alder/Nazarov Reaction of 1-Aryl-3-(trimethylsilyl) Ynones
作者:Rachael A. Carmichael、Punyanuch Sophanpanichkul、Wesley A. Chalifoux
DOI:10.1021/acs.orglett.7b00911
日期:2017.5.19
A one-pot tandem Diels–Alder/Nazarov reaction of 1-aryl-3-(trimethylsilyl) ynones has been achieved to generate carbo- and heterocyclic fused ring systems in good to excellent yields. The β-silyl effect is instrumental in accessing this otherwise challenging cascade annulation reaction. The tandem reaction proceeds in the presence of BCl3 to generate three new carbon–carbon bonds, a quaternary carbon
Cationic-Oxazaborolidine-Catalyzed Enantioselective Diels-Alder Reaction of α,β-Unsaturated Acetylenic Ketones
作者:Joshua N. Payette、Hisashi Yamamoto
DOI:10.1002/anie.200904339
日期:2009.10.12
Yne also a good dienophile: The cationic oxazaborolidine 1 promoted the formation of Diels–Alder adducts between acetylenic ketones and both cyclic and acyclic dienes in excellent yield with 99 % ee (see scheme; Tf=trifluoromethanesulfonyl, TMS=trimethylsilyl). Importantly, high levels of asymmetric induction were also observed with dienophiles that lacked the typical hydrogen‐bonding motif required