Organoboron-Promoted Regioselective Glycosylations in the Synthesis of a Saponin-Derived Pentasaccharide from Spergularia ramosa
摘要:
Organoboron-mediated regioselective glycosylations were employed as key steps in the total synthesis of a branched pentasaccharide from a saponin natural product. The ability to use organoboron activation to differentiate OH groups in an unprotected glycosyl acceptor, followed by substrate-controlled reactions of the obtained disaccharide, enabled a streamlining of the synthesis relative to a protective group-based approach. This study revealed a matching/mismatching effect of the relative configuration of donor and acceptor on the efficiency of a regioselective glycosylation reaction, a problem that was solved through the development of a novel boronic acid-amine copromoter system for glycosyl acceptor activation.
Palladium-catalyzed cross-coupling of aryl chlorides with O, N-chelate stabilized diarylborinates
作者:Nan Zhang、Chen Wang、Gang Zou、Jie Tang
DOI:10.1016/j.jorganchem.2017.05.013
日期:2017.8
diarylborinic acids in palladium catalyzed Suzuki coupling of arylchlorides. 3-Dimethylaminopropyl diarylborinates (B-5a), featuring a six-membered O, N-chelated boron ring that was confirmed by single crystal X-ray diffraction, displayed a delicately balanced stability and reactivity. Their cross-coupling with structurally various arylchlorides could be effected as efficiently as that of the parent diarylborinic
A Bond-Weakening Borinate Catalyst that Improves the Scope of the Photoredox α-C–H Alkylation of Alcohols
作者:Kounosuke Oisaki、Motomu Kanai、Kentaro Sakai
DOI:10.1055/s-0040-1707114
日期:2020.8
functionalization reactions is currently a major challenge in organicsynthesis. In this paper, a novel bond-weakening catalyst that recognizes the hydroxygroup of alcohols through formation of a borate is described. An electron-deficient borinic acid–ethanolamine complex enhances the chemical yield of the α-C–H alkylation of alcohols when used in conjunction with a photoredox catalyst and a hydrogen
2-(N-Alkylamino)-1-(trifluoroacetimidoyl)vinyl ketone derivatives as potential reagents in heterocyclic synthesis
作者:L. S. Vasil’ev、M. A. Prezent、A. V. Ignatenko、V. A. Dorokhov
DOI:10.1007/s11172-008-0336-9
日期:2008.11
A reaction of 3-acetyl-4-amino-5,5,5-trifluoropent-3-en-2-one diphenylboron chelate and ammonia or primary amines affords 4-amino- or 4-alkylamino-3-trifluoroacetimidoylpent-3-en-2-ones, new reagents which can be used for the synthesis of pyrimidines with trifluoromethyl group.
Frustrated Lewis Pair Polymers as Responsive Self-Healing Gels
作者:Meng Wang、Fabio Nudelman、Rebecca R. Matthes、Michael P. Shaver
DOI:10.1021/jacs.7b07725
日期:2017.10.11
between Lewisacids and bases in frustrated Lewis pairs (FLPs), where latent reactivity makes these reagents transformative in small molecule activations and metal-free catalysis. However, their use as a platform for developing materials chemistry is unexplored. Here we report a fully macromolecular FLP, built from linear copolymers that containing either a sterically encumbered Lewis base or Lewis acid
situ formation of aryl Grignard under Barbier condition and diisopropylaminoborane as boron source allows a complete control of the addition onto the boron electrophile. Analytically pure borinicacidderivatives were produced at the gram scale without column chromatography and isolated as borinates adducts, with ethanolamine or 8-hydroxyquinoline, after workup.