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51.
A new approach for the stereoselective synthesis of polyketide precursors containing anti-1,3-diol units flanked by a variety of alkyl branches and functional groups through a Prins cyclisation and reductive cleavage sequence is described. 相似文献
52.
Heinz Paul Rolf Wessel Günter Huschert 《Monatshefte für Chemie / Chemical Monthly》1981,112(2):209-213
2-Amino-6-aryl-imidazo(2,1-b)-1,3,4-thiadiazoles (1 a-f) were condensed with 1,3-ketocarboxylates e. g. ethyl-butyroacetate, ethyl-benzoylacetate, 4-nitrobenzoylacetate or ethyl-cyclopentanone(2)-carboxylate and ethyl-cyclohexanone(2)-carboxylate directly to imidazo(2,1-b)-1,3,4-thiadiazolo(3,2-a) pyrimidones-(6) (4 a-f, 5 a-f, 6 d, e, 7 a-f, 8 a, d).
11. Mitt. über Heterocyclen; 10. Mitt.Paul, H., Sitte, A., Wessel, R., Arch. Pharm. (Weinheim), im Druck. 相似文献
53.
The tricyclic natural products ialibinone A and ialibinone B were prepared as a 41:59 mixture in four steps starting from phloroglucinol. The synthetic sequence involved (i) acylation of phloroglucinol under Friedel-Crafts conditions, (ii) double prenylation using phase-transfer methodology, (iii) dearomatising methylation, and (iv) oxidative free radical cyclisation using manganese(III) acetate. 相似文献
54.
Caroline Roe 《Tetrahedron letters》2010,51(4):591-3550
Acid-catalysed solvolysis procedures exchange protecting groups on benzyl alcohol derivatives in the synthesis of η5 1-arylcyclohexadienyliron building blocks for alkaloid synthesis. The reaction proceeds via a carbocation intermediate which can also be intercepted by intramolecular electrophilic addition to the tricarbonyl(η4-diene)iron(0) moiety to provide a novel and high-yielding cyclisation reaction forming a 5aα-cyanomethyl-5a,8a-dihydrofluorene tricarbonyliron complex in 96% yield. 相似文献
55.
J.S. Yadav P. Purushothama Rao M. Sridhar Reddy N. Venkateswar Rao A.R. Prasad 《Tetrahedron letters》2007,48(8):1469-1471
A highly stereoselective synthesis of (+)-cryptocarya diacetate is achieved through our recently developed strategy for the construction of 1,3-diols via Prins cyclisation. The route relies mainly on the reductive cleavage of allylic ethers, ozonolysis and Wittig olefination along with Prins cyclisation. 相似文献
56.
Nityagopal Mondal Sannyasi Charan Mandal Gourab Kanti Das 《Journal of Molecular Structure》2004,680(1-3):73-81
Methyl and methoxy substituted transition states (TS) of Type-II ene cyclisation have been optimized by ab-initio method and relative stability of the diastereomeric TSs have been calculated. In all TSs, equatorial substituent positions have been found to be preferred over the axial positions except for the 4′-substituted methoxy derivative, in which the methoxy group prefers to retain axial position. It has also been noted that the presence of the methoxy group(s) in other position(s) may affect the stability of axially oriented TS and thus alters the overall stereoselectivity of the reaction. 相似文献
57.
Tapas PaulAshutosh Pal Pranab Dutta GuptaDebabrata Mukherjee 《Tetrahedron letters》2003,44(4):737-740
Stereoselective total syntheses of (±)-1,14-herbertenediol (7) and (±)-tochuinyl acetate (10) and facile total syntheses of (±)-α-herbertenol (2), (±)-β-herbertenol (3) and (±)-1,4-cuparenediol (8) have been successfully accomplished involving intramolecular cyclisation of 3-aryl-3-methyl-6-bromohexanoates and in situ methylation of the resulting cyclopentanecarboxylates as the key reactions. 相似文献
58.
The indirect electroreduction of unsaturated α-bromoesters using Ni(II) complexes as electron-transfer mediators is achieved in N,N′-dimethylformamide by constant current electrolysis between a cathode and a sacrificial anode in a diaphragmless cell. Cyclic compounds are obtained in moderate to good yields in conditions that avoid the usual preparation using organotin reagents. 相似文献
59.
I.S. Marcos M.A. Cubillo S. Carballares P. Basabe A. Benéitez H.B. Broughton 《Tetrahedron》2005,61(4):977-1003
Several tri- and tetracyclic diterpenes have been synthesised from zamoranic acid. The key step is the cyclisation of a dicarbonyl 13,14-secoderivative by SmI2. 相似文献
60.
Carlos Pérez-Balado 《Tetrahedron letters》2005,46(29):4887-4890
Racemic tetrahydropyran 3 was efficiently synthesised from allylsilane 6 and aldehyde 7 via an intramolecular Sakurai cyclisation. In a single step, the relative configuration of three chiral centres was established. Allylsilane 6 was readily assembled from 1-iodo-1-selenopropene 10, a synthetic equivalent of a propene 1,1-dianion. 相似文献