Catalytic Asymmetric Synthesis of Cyclohexanes by Hydrogen Borrowing Annulations
作者:Roly J. Armstrong、Wasim M. Akhtar、Tom A. Young、Fernanda Duarte、Timothy J. Donohoe
DOI:10.1002/anie.201907514
日期:2019.9.2
Hydrogen borrowing catalysis serves as a powerful alternative to enolate alkylation, enabling the direct coupling of ketones with unactivated alcohols. However, to date, methods that enable control over the absolute stereochemical outcome of such a process have remained elusive. Here we report a catalytic asymmetric method for the synthesis of enantioenriched cyclohexanes from 1,5‐diols via hydrogen
Piperidine and Azetidine Formation by Direct Cyclization of Diols with N-Nonsubstituted Sulfonamide under the Mitsunobu Conditions Utilizing (Cyanomethylene)tributylphosphorane (CMBP) and Its Application to the Synthesis of Lupinine
our studies on the Mitsunobu chemistry, diethylazodicarboxylate (DEAD)-PPh3 and our new azodicarboxamide reagents, e.g., N,N,N’,N’-tetramethylazodicarboxamide (TMAD)-PBu3 could not promote alkylation of N-nonsubstituted sulfonamides such as TsNH2, because the amide reacted with PPh3 or PBu3 to form triphenylor tributylphosphine tosylimide (TsN=PR3) under the reaction conditions. Furthermore, the same
3-Chloropropyl and 4-Chlorobutyl Phenyl Ethers as Sources of 1,3-Dilithiopropane and 1,4-Dilithiobutane: Sequential Reaction with Carbonyl Compounds
作者:Francisco Foubelo、Sadiq A. Saleh、Miguel Yus
DOI:10.1021/jo000039m
日期:2000.6.1
The reaction of 3-chloropropyl and 4-chlorobutyl phenyl ethers (1) with lithium powder and a catalytic amount of DTBB (5% molar) in THF at -78 degrees C followed by successive treatment with a carbonyl compound [(RRCO)-R-1-C-2 = (BuCHO)-C-t, Me2CO, (CH2)(5)CO, (-)-menthone] at -78 to 20 degrees C and, after 1.5 h at this temperature, with a second one [(RRCO)-R-3-C-4 = (BuCHO)-C-t, PhCHO, Me2CO, MeCOPrn, (CH2)(5)CO, (-)-menthone] at -78 degrees C leads,after hydrolysis with water, to the corresponding 1,5- and 1,6-diols (2). Because of the competition of two different reductive cleavages, 1,4- and 1,5-diols 3 were also obtained as side-reaction products.
Chemo- and Regioselective Synthesis of Acyl-Cyclohexenes by a Tandem Acceptorless Dehydrogenation-[1,5]-Hydride Shift Cascade
作者:Lewis B. Smith、Roly J. Armstrong、Daniel Matheau-Raven、Timothy J. Donohoe
DOI:10.1021/jacs.9b12296
日期:2020.2.5
acceptorless dehydrogenation of the diol followed by a redox-neutral cascade process, which is independent of the iridium catalyst. Deuteriumlabelingstudies established that the key step of this cascade involves a novel base-mediated [1,5]-hydride shift. The cyclohexenyl ketone products could readily be cleaved under mildly acidic conditions to access a range of valuable substituted cyclohexene derivatives
描述了一种从五甲基苯乙酮和 1,5-二醇中获得取代的酰基环己烯的原子经济方法。该过程由铱 (I) 催化剂与庞大的富电子膦配体 (CataCXium A) 共同催化,该配体有利于无受体脱氢反应,而不是共轭还原成相应的环己烷。该反应产生水和氢气作为唯一的副产物,并且可以使用该方法以非常高的产率合成范围广泛的官能化酰基环己烯产物。进行了一系列对照实验,结果表明该过程是由二醇的无受体脱氢引发的,然后是氧化还原中性级联过程,该过程与铱催化剂无关。氘标记研究表明,该级联的关键步骤涉及一种新型碱介导的 [1,5]-氢化物转移。环己烯基酮产物在弱酸性条件下很容易裂解,以获得一系列有价值的取代环己烯衍生物。