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2.
Biswanath Das Maddeboina Krishnaiah Katta Venkateswarlu Vtukuri Saidi Reddy 《Helvetica chimica acta》2007,90(1):110-113
Oxiranes and aziridines efficiently undergo ring opening with bismuth nitrate at room temperature to furnish the corresponding β‐(nitrooxy)‐substituted alcohols and amines respectively. The conversions are highly regio‐ and stereoselective and afford the nitrooxy‐compounds in excellent yields within a short period of time. 相似文献
3.
Qi‐Lun Liu Di‐Di Wen Chen‐Chen Hang Qiu‐Lian Li Yong‐Ming Zhu 《Helvetica chimica acta》2010,93(7):1350-1354
1‐Aryl‐1H‐benzotriazole derivatives were synthesized via intramolecular cyclization of easily obtained triazenes, using CuI as the catalyst, DMSO as the solvent, t‐BuONa as the base, and 1,10‐phenanthroline as the ligand, in up to 97% yield. The synthesis is regiospecific and functional group‐tolerant. 相似文献
4.
A series of novel β‐lactams derived from natural gallic acid were conveniently synthesized via classical Staudinger ketene‐imine cycloaddition reaction. Their structures were confirmed by satisfactory analytical and spectroscopic methods. The preliminary bioassay showed that some of the target compounds exhibited obvious insecticidal activity against Heliothis armigera at the dosage of 0.2 mg/mL. 相似文献
5.
Yangxue Liu Sultan Ahmed Xiao‐Yan Qin Hossein Rouh Guanzhao Wu Guigen Li Bo Jiang 《化学:亚洲杂志》2020,15(7):1125-1131
An effective chiral GAP methodology for preparing α‐aminomethyl enaminones through a (R)‐CSA‐catalyzed asymmetric aza‐Baylis‐Hillman reaction is reported. Excellent yields and high diastereoselectivity could be obtained under mild conditions and convenient GAP techniques. The confirmations of the absolute configuration of N‐phosphonyl imine and chiral enaminone by X‐ray diffraction provides an explicit explanation of the chirality mechanism for GAP chemistry. 相似文献
6.
A diastereoselective coupling of dimethyl malonate with N‐(tert‐butyl)sulfinyl imines under solvent‐free conditions was developed, using NaHCO3 or NaI as base promoters. The resulting dimethyl 2‐(1‐aminoalkyl)malonates could be easily transformed successively to β‐amino esters and the corresponding β‐lactams with high optical purity. 相似文献
7.
Scott R. Gilbertson Omar D. Lopez 《Angewandte Chemie (International ed. in English)》1999,38(8):1116-1119
Kinetic resolution is achieved in the reaction of racemic diiron complexes like 1 with the chiral nitrone (−)- 2 . Oxidative removal of the metal and reductive cleavage of the N−O bond provides β-amino acids. This sequence was used in the synthesis of β-amino acids as well as the corresponding β-lactams 4 (via 3 ). 相似文献
8.
Gowravaram Sabitha Rangavajjula Srinivas Peddabuddi Gopal M. Bhikshapathi Jhillu Singh Yadav 《Helvetica chimica acta》2011,94(1):119-121
Bismuth(III) chloride was found to be an efficient catalyst for the transesterification of a variety of β‐keto esters with a wide range of alcohols to afford transesterified products in good to high yields in short reaction times (see Table). 相似文献
9.
Manganese(III)‐promoted cyclization of N‐alkenylmalonamides (=N‐alkenylpropanediamides) gave 3‐(aryl/(alkylamino)carbonyl) β‐lactams as well as 3‐(aryl/(alkylamino)thiocarbonyl) β‐lactams. The relative configuration of the obtained products was unambiguously determined by X‐ray crystallography. The proposed method is very useful for the one‐pot synthesis of a number of 3‐(aryl/(alkylamino)carbonyl) β‐lactams, especially those containing an amino(thiocarbonyl) moiety, which are not selectively accessible by other methods. 相似文献
10.
LI Wei HUANG Hai JIN Xiaodong LIU Yujian XU Chaohang ZHU Hongjun 《高等学校化学研究》2014,30(5):770-773
The authors described a short and highly enantioselective route to (R)-salmeterol involving asymmetric synthesis of cyanohydrin followed by nucleophilic substitution with 6-(4-phenylbutoxy) hexyl methanesulfonate. 相似文献
11.
Asymmetric Synthesis of Spirocyclic β‐Lactams through Copper‐Catalyzed Kinugasa/Michael Domino Reactions 下载免费PDF全文
Tao Shu Long Zhao Sun Li Dr. Xiang‐Yu Chen Dr. Carolina von Essen Prof. Dr. Kari Rissanen Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2018,57(34):10985-10988
The first copper‐catalyzed highly chemo‐, regio‐, diastereo‐, and enantioselective Kinugasa/Michael domino reaction for the desymmetrization of prochiral cyclohexadienones is described. In the presence of a chiral copper catalyst, alkyne‐tethered cyclohexadienones couple with nitrones to generate the chiral spirocyclic lactams with excellent stereoselectivity (up to 97 % ee, >20:1 dr). The new method provides direct access to versatile highly functionalized spirocyclic β‐lactams possessing four contiguous stereocenters, including one quaternary and one tetra‐substituted stereocenter. 相似文献
12.
Yaping Wang Walter Weissensteiner Kurt Mereiter Felix Spindler 《Helvetica chimica acta》2006,89(8):1772-1782
The two diphosphine ligands (Rp,Rp)‐ and (Sp,Sp)‐bis[2‐(diphenylphospino)ferrocenyl]methane, (Rp,Rp)‐ and (Sp,Sp)‐ 1 , resp., were prepared in six steps from (S)‐ and (R)‐ferrocenyl tolyl sulfoxide, respectively (Scheme). In the solid state, both the diborane complex (Rp,Rp)‐ 1 ? (BH3)2 and the palladium dichloride complex [PdCl2((Rp,Rp)‐ 1 )] were found to adopt C2‐pseudosymmetric structures according to X‐ray analyses (Figs. 2 and 3). In the Rh‐ and Ru‐catalyzed hydrogenation of selected alkenes and ketones in the presence of the new ligands, enantioselectivities of up to 55% ee were obtained. 相似文献
13.
A series of α‐(fluoro‐substituted phenyl)pyridines have been synthesized by means of a palladium‐catalyzed cross‐coupling reaction between fluoro‐substituted phenylboronic acid and 2‐bromopyridine or its derivatives. The reactivities of the phenylboronic acids containing di‐ and tri‐fluoro substituents with α‐pyridyl bromide were investigated in different catalyst systems. Unsuccessful results were observed in the Pd/C and PPh3 catalyst system due to phenylboronic acid containing electron‐withdrawing F atom(s). For the catalyst system of Pd(OAc)2/PPh3, the reactions gave moderate yields of 55% –80%, meanwhile, affording 10% –20% of dimerisation (self‐coupling) by‐products, but trace products were obtained in coupling with 2,4‐difluorophenylboronic acids because of steric hinderance. Pd(PPh3)4 was more reactive for boronic acids with sterically hindering F atom(s), and the coupling reactions gave good yields of 90% and 91% without any self‐coupling by‐product. 相似文献
14.
Bartomiej Furman Ren Thürmer Zbigniew Kaua Robert ysek Wolfgang Voelter Marek Chmielewski 《Angewandte Chemie (International ed. in English)》1999,38(8):1121-1123
Despite the antibiotic activity and the attractiveness of β-lactams, the solid-phase synthesis of this class of compounds has been barely reported. Now the diastereoselective synthesis of the 1-oxacepham 2 from the resin-bound β-lactam derivative 1 has been achieved in five steps. The synthesis of 2 and other 1-oxacephams is attractive because all the reaction steps proceed in high yield, the purity of the product is high, and the reaction sequence is simple. 相似文献
15.
Isoflavone derivatives were synthesized via intramolecular cyclization of 3‐(2‐bromophenyl)‐3‐oxopropanal derivatives, using CuI as the catalyst, 2‐picolinic acid (=pyridine‐2‐carboxylic acid) as the ligand, K2CO3 as the base, and DMF as the solvent, in up to 96% yield. The synthesis is functional group‐tolerant. 相似文献
16.
Chunhui Gu Jiaojiao Zhai Jianan Jiang Hongwei Liu Lei Wang Dunru Zhu Yafei Ji 《中国化学》2014,32(2):179-190
The treatment of α‐bromoalkyl aryl ketones and 2‐(propan‐2‐ylidene)hydrazine carbothioamide afforded 4‐aryl‐2‐(2‐(propan‐2‐ylidene)hydrazinyl)thiazoles via a Hantzsch‐thiazole synthesis, which reacted with 4‐aryl‐2,4‐diketoesters via a sequential Knorr‐pyrazole reaction to deliver a variety of aryl‐substituted ethyl 1‐(thiazol‐2‐yl)‐1H‐pyrazole‐3‐carboxylates in a one‐pot fashion with moderate to high yields. The key intermediates 4‐aryl‐2,4‐diketoesters, existing as its enolic lithium salt, were synthesized in situ by a high‐yield tert‐BuOLi‐mediated Claisen condensation of alkylphenones and diethyl oxalate. This class of elegant molecule comprises aryl groups on the two different heterocyclic cores, and the configurations of two representative molecules were determined by single crystal X‐ray crystallography. 相似文献
17.
Zhenling Chen Dr. Lili Lin Min Wang Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7561-7567
The asymmetric Kinugasa reaction was performed on pure water for the first time without the need for any organic co‐solvents. In contrast to most asymmetric Kinugasa reactions, trans‐β‐lactams were obtained as the major products in good yields, enantioselectivities, and diastereoselectivities (up to 90 % yield, 98 % ee, and >99:1 d.r.). This reaction is atom‐economical, environmentally friendly, and affords synthetically useful but challenging products. 相似文献
18.
Enantiomerically pure iridium complexes with phosphino‐ and (phosphinooxy)‐substituted N‐heterocyclic carbene (NHC) ligands were synthesized. Investigation of their electronic properties showed a similar trans influence of the phosphino (or phosphinooxy) and the NHC units. The complexes were tested in iridium‐catalyzed hydrogenation. While low conversions were observed with unfunctionalized olefins, the catalysts proved to be suitable for hydrogenation of the α,β‐unsaturated ester 20 , allylic alcohol 21 , and imine 22 . The enantioselectivities were, however, moderate. 相似文献
19.
Ekaterina A. Koneva Konstantin P. Volcho Yuri V. Gatilov Dina V. Korchagina Georgi E. Salnikov Nariman F. Salakhutdinov 《Helvetica chimica acta》2008,91(10):1849-1856
The reaction of (+)‐car‐2‐ene ( 4 ) with chlorosulfonyl isocyanate (=sulfuryl chloride isocyanate; ClSO2NCO) led to the tricyclic lactams 6 and 8 corresponding to the initial formation both of the tertiary carbenium and α‐cyclopropylcarbenium ions (Scheme 2). A number of optically active derivatives of β‐amino acids which are promising compounds for further use in asymmetric synthesis were synthesized from the lactams (see 16, 17 , and 19 – 21 in Scheme 3). 相似文献
20.
Luis G. Hernández‐Vázquez Marco A. Leyva Alejandro J. Metta‐Magaña Jaime Escalante 《Helvetica chimica acta》2012,95(11):2218-2230
Different cyclo‐β‐dipeptides were prepared from corresponding N‐substituted β‐alanine derivatives under mild conditions using PhPOCl2 as activating agent in benzene and Et3N as base. To evaluate β3‐substituent influence, the amino acids 7 – 26 were synthesized, and a β‐lactam formation reaction was carried out instead of cyclo‐β‐dipeptide formation. The crystal structures of three derivatives of cyclo‐β‐peptides and one β‐lactam are presented. 相似文献