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51.
Vera J. Meyer Prof. Dr. Meike Niggemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4687-4691
A calcium‐catalyzed direct reduction of propargylic alcohols and ethers has been accomplished by using triethylsilane as a nucleophilic hydride source. At room temperature a variety of secondary propargylic alcohols was deoxygenated to the corresponding hydrocarbons in excellent yields. Furthermore, for the first time, a catalytic deoxygenation of tertiary propargylic alcohols was generally applicable. The same protocol was suitable for an efficient reduction of secondary as well as tertiary propargylic methyl, benzyl and allyl ethers. Substrates containing an additional keto‐, ester or secondary hydroxyl function were reduced with exceptional chemoselectivity at the propargylic position. 相似文献
52.
Turn sugar into oil: The deoxygenation reaction of sugar moieties is important for the conversion of biomass into chemicals and fuels. The methyltrioxorhenium-catalyzed deoxydehydration reaction was successfully applied to this purpose using another alcohol as solvent/reductant. The reaction was highly stereospecific, affording linear polyene products from C(4) -C(6) sugar alcohols and aromatic compounds from C(4) -C(6) sugars. 相似文献
53.
Deeb Taher Prof. Dr. Michelle E. Thibault Domenico Di Mondo Michael Jennings Marcel Schlaf Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10132-10143
The ruthenium aqua complexes [Ru(H2O)2(bipy)2](OTf)2, [cis‐Ru(6,6′‐Cl2‐bipy)2(OH2)2](OTf)2, [Ru(H2O)2(phen)2](OTf)2, [Ru(H2O)3(2,2′:6′,2′′‐terpy)](OTf)2 and [Ru(H2O)3(Phterpy)](OTf)2 (bipy=2,2′‐bipyridine; OTf?=triflate; phen=phenanthroline; terpy= terpyridine; Phterpy=4′‐phenyl‐2,2′:6′,2′′‐terpyridine) are water‐ and acid‐stable catalysts for the hydrogenation of aldehydes and ketones in sulfolane solution. In the presence of HOS(O)2CF3 (triflic acid) as a dehydration co‐catalyst they directly convert 1,2‐hexanediol to n‐hexanol and hexane. The terpyridine complexes are stable and active as catalysts at temperatures ≥250 °C and in either aqueous sulfolane solution or pure water convert glycerol into n‐propanol and ultimately propane as the final reaction product in up to quantitative yield. For the terpy complexes the active catalyst is postulated to be a carbonyl species [(4′‐R‐2,2′:6′,2′′‐terpy)Ru(CO)(H2O)2](OTf)2 (R=H, Ph) formed by the decarbonylation of aldehydes (hexanal for 1,2‐hexanediol and 3‐hydroxypropanal for glycerol) generated in the reaction mixture through acid‐catalyzed dehydration. The structure of the dimeric complex [{(4′‐phenyl‐2,2′:6′,2′′‐terpy)Ru(CO)}2(μ‐OCH3)2](OTf)2 has been determined by single crystal X‐ray crystallography (Space group P (a=8.2532(17); b=12.858(3); c=14.363(3) Å; α=64.38(3); β=77.26(3); γ = 87.12(3)°, R=4.36 %). 相似文献
54.
NanYanFU XueMeiZHAO YaoFengYUAN JiTaoWANG 《中国化学快报》2003,14(10):1018-1020
The reductive deoxygenation of aldehydes and ketones into the corresponding alkanes is accomplished by LiAlH4 in the presence of Lewis acid InBr3. It provides a convenient method to complete the transformation from carbonyl compounds to alkanes. 相似文献
55.
Entry into Major Groups Retaining Taxol via Sinenxan A 总被引:3,自引:0,他引:3
Compound 1 as a key intermediate of 1,7,9-trideoxytaxol was synthesized in ten steps from a biosynthetically available taxane,Sinenxan A. The key steps in the synthesis were deoxygenation at C-14,allylic oxidation at C-13 and construction of the oxetane ring. 相似文献
56.
Jun Ishihara Yohei IkumaSusumi Hatakeyama Takanori SuzukiAkio Murai 《Tetrahedron》2003,59(51):10287-10294
Azadirachtin is a C-seco limonoid, derived from the neem tree. Previously, we reported the synthesis of the right and left segments of azadirachtin, in addition to the coupling reaction of the modeled ester utilizing Claisen rearrangement. Herein we report the transformation of the modeled rearrangement product into a tricyclic dihydrofuran, which would be expected to have bioactivity against insects. 相似文献
57.
Quinazolin-1-oxides were prepared by the oxidation of tetrahydroquinazolines with H2O2-tungstate and their ambient light photochemistry was investigated. Substituent effects on their photochemical cyclization and the reactions of the products 1aH-[1,2]oxazireno[2,3-a]quinazolines under photochemical and thermal conditions are reported. The cyclization of quinazolin-1-oxides and the reactions of 1aH-[1,2]oxazireno[2,3-a]quinazolines show pronounced solvent isotope and solvent effects. 相似文献
58.
亚砜是有机合成的重要中间体,但反应完成后,往往需要除去亚砜基团,通常的方法是将亚砜脱氧为硫醚,再用Raney镍等除去硫醚基团: 相似文献
59.
60.
The Barton-McCombie deoxygenation is a landmark reaction in organic chemistry. Its efficiency in generating carbon radicals from alcohols is unmatched, despite the passage of more than 40 years since its discovery. Its mechanism, far from being straightforward, is in fact quite subtle and conceptually part of a much larger family of very powerful thiocarbonyl controlled radical reactions. This general mechanistic manifold encompasses the degenerate transfer of xanthates and related thiocarbonylthio congeners, a process that also subtends the now popular RAFT/MADIX polymerization technology, the remarkably versatile Barton decarboxylation via thiohydroxamate esters, the generation of nitrogen-centered radicals from oxime xanthates and thiosemicarbazones and thiosemicarbazides, and certainly other transformations that will emerge in the coming years. The present overview retraces the history of the Barton-McCombie reaction, the evolution of the mechanistic aspects and the resulting consequences in terms of new transformations and synthetic applications. 相似文献