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111.
The ring expansion reactions of unactivated alkynylcyclopropanes X‐C≡C‐C3H5 → X‐C=C4H5 (X = H, F, Cl, Me, OMe, NMe2, CMe3) were examined using the density functional theory calculations. All of the structures were completely optimized at the B3LYP/6‐311++G** level of theory. For clarify the effect of the cationic gold(I), we also added AuPH3+ as the catalyst into the system and the structures for Au were calculated at the B3LYP/LANL2DZ level of theory. The main finding of this work is that the singlet‐triplet splitting of X‐C≡C‐C3H5 play an important role in determining the kinetic and thermodynamic stability of the unactivated ring expansion reactions. When X‐C≡C‐C3H5 with a smaller singlet‐triplet splitting is utilized, the reaction has a smaller activation energy and a larger exothermicity. 相似文献
112.
Surfactant (SDS)‐mediated cleavage of imines was achieved with acetic anhydride to the corresponding carbonyls (aldehydes and ketones) and acetanilides in water at 25–30°C with very good to excellent yields, thus contributing significantly to the green chemistry concept. 相似文献
113.
Sankareswaran Srimurugan Paulsamy Suresh Thirukkallam Kanthadai Varadarajan 《合成通讯》2013,43(15):2483-2490
A facile method for the synthesis of (2R,3R)‐1,4‐dimethoxy‐1,1,4,4‐tetrasubstituted‐2,3‐butanediols involving oxidative cleavage of benzylidene acetal as a key step is described. These sterically hindered diols unusually formed cyclic sulfites as the major product under methanesulfonylation reaction conditions. 相似文献
114.
115.
Isoflavonoids are a class of organic compounds that act primarily as antioxidants. They are produced almost exclusively by various members of the bean family including soybeans, tofu, peanuts, chick peas, and alfalfa. The antioxidant characteristics that isoflavonoids exhibit help hinder the progression of certain cancers, primarily breast, prostate, and colon cancer. We have developed a three-five step synthesis for obtaining a suite of isoflavonoid derivatives. The synthesis involves an enamine formation, a ring closure and halogenation, a Suzuki coupling, and finally a global deprotection to obtain the respective isoflavonoid derivatives. 相似文献
116.
Vyacheslav I. Supranovich Gennady I. Borodkin Aleksey Yu. Vorob’ev Vyacheslav G. Shubin 《Tetrahedron letters》2014
An unusual cleavage of the Cpy–Cpy bond in the reaction of 2,2′-bipyridine N,N′-diimine and its C-methyl substituted derivatives with acetylenes is described. The effect of the solvent on the yield of 7,7′-bipyrazolo[1,5-a]pyridine-2,2′,3,3′-tetracarboxylates and the products of cleavage of the Cpy–Cpy bond has been studied. The mechanism of the cleavage reaction is discussed on the basis of DFT calculations. 相似文献
117.
Fe(Cp)2BF4 is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)2BF4 as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol. 相似文献
118.
A ring fragmentation and intramolecular azomethine ylide 1,3-dipolar cycloaddition sequence of reactions was successfully used in the preparation of a known (±)-cycloclavine precursor in good overall yield. Results of efforts to incorporate the tetrasubstituted cyclopropane ring present in cycloclavine are also discussed. 相似文献
119.
Piyasena Hewawasam Yong TuThomas W. Hudyma Xiaofan ZhangRobert G. Gentles John F. KadowNicholas A. Meanwell 《Tetrahedron letters》2014
A convenient and practical synthesis of 6-carboalkoxy-13-cycloalkyl-5H-indolo[2,1-a][2]benzazepine-10-carboxylic acid derivatives (6) has been developed. The key step in the synthesis utilizes an intramolecular tandem reaction sequence of a Michael addition followed by a Horner–Wadsworth–Emmons (HWE) olefination reaction between hemi-aminal 11 and methyl 2-(dimethoxyphosphoryl)acrylate 12. The ring construction occurred efficiently and purification of the products 6 was straightforward. The C-10 methyl ester of 6a was hydrolyzed selectively to the carboxylic acid 13 while the olefin of 6d was converted to the cyclopropane 14 using trimethylsulfoxonium iodide in DMSO in the presence of NaH. 相似文献
120.