Direct synthesis of substituted tetrahydrofurans via regioselective dehydrative polyol cyclization cascades
摘要:
A one-pot procedure for the conversion of 1,2,4,5-tetraols into substituted tetrahydrofuran moieties has been developed. This involves the regioselective sulfonylation of the terminal hydroxyl of the polyol array followed by sequential oxirane and oxolane formation under basic conditions. A survey of reaction conditions has defined the use of N-(2,4,6-triisopropylbenzenesulfonyl)imidazole as sulfonylation reagent, potassium tert-butoxide as base, and tert-butanol as solvent to be optimal. Under these conditions, 8-O-benzyl-octan-1,2,4,5,8-pentaol was converted stereospecifically into tetrahydrofurans in 62% yield. Polyol substrates were derived from Sharpless asymmetric dihydroxylation of 1,4-dienes. Hence, substituted tetrahydrofurans could be obtained stereospecifically from diene substrates in two operations. (C) 2002 Elsevier Science Ltd. All rights reserved.
The organocuprates derived from reaction of Grignard reagents with CuBr·Me2S react with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran via a 1,2-metallate rearrangement to generate an alkenylmagnesium cuprate.
[EN] COMPOUNDS FOR OPTICALLY ACTIVE DEVICES<br/>[FR] COMPOSÉS POUR DISPOSITIFS OPTIQUEMENT ACTIFS
申请人:MERCK PATENT GMBH
公开号:WO2017032442A1
公开(公告)日:2017-03-02
The present invention relates to novel compounds, particularly to compounds comprising a photoactive unit, said novel compounds being particularly suitable for ophthalmic devices as well as to ophthalmic devices comprising such compounds.
Nucleophile Coordination Enabled Regioselectivity in Palladium‐Catalyzed Asymmetric Allylic C−H Alkylation
作者:Lian‐Feng Fan、Shi‐Wei Luo、Shu‐Sen Chen、Tian‐Ci Wang、Pu‐Sheng Wang、Liu‐Zhu Gong
DOI:10.1002/anie.201908960
日期:2019.11.18
Branched selectivity in asymmetric allylic C-H alkylation is enabled by using 2-acylimidazoles as nucleophiles in the presence of a chiral phosphoramidite-palladium catalyst. A wide range of terminal alkenes, including 1,4-dienes and allylarenes, are nicely tolerated and provide chiral 2-acylimidazoles in moderate to high yields and with high levels of regio-, and enantio-, and E/Z-selectivities. Mechanistic
作者:Natalie N. M. Nguyen、Mathieu Leclère、Nicole Stogaitis、Alex G. Fallis
DOI:10.1021/ol100150f
日期:2010.4.16
A general route to linear triquinanes including a formal synthesis of (±)-Δ9(12)-capnellene is described. This cascade strategy combines an intramolecular Diels−Alder reaction tandem metathesis protocol to generate the linear cis-anti-cis-tricyclo[6.3.0.02,6]undecane skeleton directly. Significantly, the ring-closing−ring-opening−cross-metathesis (RCM−ROM−CM) sequence with our norbornene adducts is
[EN] HYDROPHILIC COMPOUNDS FOR OPTICALLY ACTIVE DEVICES<br/>[FR] COMPOSÉS HYDROPHILES POUR DISPOSITIFS OPTIQUEMENT ACTIFS
申请人:MERCK PATENT GMBH
公开号:WO2018149853A1
公开(公告)日:2018-08-23
The present invention relates to novel compounds, particularly to compounds comprising a photoactive unit, said novel compounds being particularly suitable for compositions and ophthalmic devices as well as to compositions and ophthalmic devices comprising such compounds.