Palladium-catalysed reactions of 6-halogeno-1,1′-binaphthyl derivatives. A detailed investigation of structure/reactivity and structure/selectivity relationships

Five 6-halogeno-binaphthyl derivatives of different structure were synthesised starting from 2,2′-dihydroxy-1,1′-binaphthyl 1. Several new 6-substituted binaphthyl compounds were obtained via the palladium-catalysed reactions of these derivatives. The reactivity of 6-iodo derivatives was much greater in most cases. In cross-coupling reactions the 6-bromo compounds were converted into the products using longer reaction times and/or higher temperatures. The reactivity difference between the two types of substrates was especially marked in aminocarbonylation and Heck reactions.     

尿素羰基化作用研究进展

综述了尿素作为羰基化试剂合成氨基酸酯或碳酸酯类化合物及脲类化合物的研究进展,详细讨论了合成反应中所涉及的催化剂、反应机理和工艺条件,指出通过尿素醇解或胺解反应合成相应化合物是一条绿色工艺路线,具有广阔应用前景.     

Synthesis of (E)-2-(1-ferrocenylmethylidene)malonic acid derivatives by a cobalt-catalyzed domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines

The domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines was investigated in the presence of Co₂(CO)₈ as catalyst. In most cases the main products are 2-(1-ferrocenylmethylidene) malonates formed by an N(1)-C(4) cleavage of the primarily derived β-lactams. The latter compounds could only be isolated when the reaction was carried out at relatively low CO pressure, using an excess of ethyl diazoacetate. trans-N-(tert-Butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam proved to be the most stable one among these compounds and could be isolated in 55% yield. N-alkyl β-lactams were shown to undergo acidic cleavage leading to the E isomers of 2-(1-ferrocenylmethylidene) malonates as the main products. The structures of the two new compounds, (E)-2-ethoxycarbonyl-3-ferrocenyl-N-((R)-1-phenylethyl)-2-propenamide and trans-N-(tert-butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam were confirmed by X-ray crystallography. The relative thermodynamical stability of the products as well as the energetics of the acid-mediated cleavage of the β-lactam ring was elucidated with DFT calculations.     

Iridium-catalyzed enantioselective Pauson-Khand-type reaction of 1,6-enynes

Iridium-chiral diphosphine complex catalyzes an enantioselective intramolecular Pauson-Khand-type reaction to give various chiral bicyclic cyclopentenones. The enantioselective reaction proceeds more smoothly and enantioselectively under a lower partial pressure of carbon monoxide. Moreover, aldehyde can be used as a CO source in the enantioselective carbonylative coupling.     

The palladium-phenanthroline catalyzed carbonylation of nitroarenes to diarylureas: Effect of chloride and diphenylphosphinic acid

The application of the palladium-phenanthroline catalytic system to the carbonylation of nitrobenzene in the presence of aniline to afford diphenylurea has been investigated. The reaction is best performed with equimolar amounts of the two reagents. Use of higher concentrations of either aniline or nitrobenzene or an increase in temperature in the range 120-170 °C leads to the formation of higher amounts of azo- and azoxybenzene. The latter were found to contain exclusively the aryl moiety deriving from nitrobenzene, with no inclusion of that derived from aniline. The addition of a small amount of diphenylphosphinic acid doubles the conversion and improves the selectivity in diphenylurea, but the effect is attenuated for larger amounts of acid. Small amounts of chloride, of the order of 10-30 mol% with respect to palladium, improve both rate and selectivity, but only inhibiting effects are detected when chloride is added to the reaction mixture for the carbonylation of 2,4-dinitrotoluene to dimethyl 2,4-toluenedicarbamate. The data obtained and that previously reported in the literature has been analyzed in the context of a unifying mechanism and an explanation for some apparent contradictions has been given.     

Synthesis of acridones through palladium-catalyzed carbonylative of 2-bromo-diarylamines

A facile protocol for the synthesis of acridone derivatives has been developed through palladium-catalyzed carbonylation/CH activation sequence from 2-bromo-diarylamines in moderate to excellent yields. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates converted to the corresponding acridones.     

Synthesis of (+)-altholactone, (+)-7-epi-altholactone, (−)-etharvensin,and (+)-alumheptolide-A using Pd-catalyzed carbonylation

Syntheses of (+)-altholactone isolated from Goniothalamus giganteus and its C-7 epimer (+)-7-epi-altholactone, (?)-etharvensin and (+)-alumheptolide-A were achieved. The lactone ring of these compounds was constructed using Pd-catalyzed carbonylation.     

Asymmetric cyclization-carbonylation of 2-alkyl-2-propargylcyclohexane-1,3-diones: facile access to optically active hydrindanes

Oxidative cyclization-carbonylation of 2-alkyl-2-propargylcyclohexane-1,3-diones mediated by Pd(TFA)₂/2,2′-isopropylidenebis[(4R)-4-(3,4-dimethoxyphenyl)-2-oxazoline] 28 afforded bicyclic-β-alkoxyacrylates in 51-74% yields with 72-82% ee. The products containing quaternary carbon were converted to optically active hydrindanes 33.     

Pd-Catalyzed Asymmetric 5-exo-trig Cyclization/Cyclopropanation/Carbonylation of 1,6-Enynes for the Construction of Chiral 3-Azabicyclo[3.1.0]hexanes

We herein disclose a mild and efficient access to chiral 3-azabicyclo[3.1.0]hexanes via a Pd-catalyzed asymmetric 5-exo-trig cyclization/cyclopropanation/carbonylation of 1,6-enynes. Various nucleophiles, such as alcohols, phenols, amines and water, are well compatible with the reaction system. This reaction forms three C−C bonds, two rings, two adjacent quaternary carbon stereocenters as well as one C−O/C−N bond with excellent regio- and enantioselectivities. The products could be further functionalized to generate a library of 3-azabicyclo[3.1.0]hexane frameworks.     

二氧化碳和胺催化合成甲酰胺反应研究

二氧化碳是碳资源利用的最终形式,也是一种绿色的碳一资源。通过催化化学的方法将二氧化碳转化为高附加值精细化学品是二氧化碳循环利用的有效途径。酰胺类化合物是一类重要的化工原料和溶剂,广泛应用于医药、农药、日用化学品及石油化工等众多领域且需求量巨大。因此,以二氧化碳为羰源,通过高效催化体系的建立实现二氧化碳与胺反应合成甲酰胺具有重要意义。本文分别从催化体系、还原剂和反应机理等角度综述了这一领域近年来的主要研究成果。其中,催化体系可分为贵金属催化剂如Ir、Pd、Pt、Ru、Rh,非贵金属催化剂如Ni、Mo、Cu、Fe、Co、Zn、Al,有机分子催化剂和无催化剂体系,常用的还原剂为H₂,硅烷和硼烷。在此基础上,对不同催化体系的典型反应机理进行了讨论。