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31.
32.
Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane- and phosphite-borane adducts by means of simple alcoholysis without the use of molecular sieves as a catalyst. Phosphane-boranes bearing at least one aromatic substituent are readily deprotected in high yields. Borane complexes of trialkylphosphanes or phosphites, however, cannot be deprotected in this way. The main merit of our method is its simplicity: apart from evaporation of the solvent, no further work-up or purification is needed. 相似文献
33.
Almir S. Gazizov Andrey V. Smolobochkin Ekaterina A. Anikina Julia K. Voronina Alexander R. Burilov Michail A. Pudovik 《合成通讯》2017,47(1):44-52
Herein we report our studies on the acid-catalyzed cyclisation of N-(4,4-diethoxybutyl)sulfonamides at the presence of polyatomic phenols as an efficient one-pot approach to the synthesis of 1-sulfonyl-2-arylpyrrolidines from the acyclic precursors. 相似文献
34.
Burkhardt I. Wilke 《Tetrahedron letters》2010,51(52):6871-6873
Derivatives of camphorsultam which contain novel spirooxazolidine and spirooxazine structures have been prepared in high yield and purity. Though it was expected that the ketone moiety would undergo acetal formation, the imine instead underwent reaction and was proven by X-ray crystallography and 2D NMR techniques. The initial ketone-containing derivatives were then reduced to produce exo-hydroxy analogs that have potential as a new family of chiral auxiliaries. 相似文献
35.
Shengjun Huang Jun Liao Qingjie Zhao Xiaoyun Chai Baogang Wang Shichong Yu 《Journal of carbohydrate chemistry》2013,32(2):158-168
TMSCl was shown to be an efficient reagent for selective deprotection of the anomeric position protected as N,O-dimethylhydroxylamine glycoside. This deprotection condition was proved to be compatible with a number of protecting groups, such as the TBDPS, acetyl, benzyl, benzylidene, and benzoyl groups. 相似文献
36.
Methyl (8R,13S)-8α,13:13,17-diepoxy-14,15-dinorlabdane-19-oate, easily prepared from communic acids, is a suitable intermediate for synthesizing pentacyclic quassinoids, because it enables the elaboration of the A ring and the further construction of the B-C-D ring system of these terpenoids. The cetal group is stable under the reaction conditions utilized during the elimination of the ester group and the introduction of the hydroxyl group on C-3. At the same time, it enables the regeneration of the methylketone and exocyclic double bond presented by methyl 13-oxo-14,15-dinorlabd-8(17)en-19-oate. The latter compound was previously used to construct the B-C-D-ring of these quassinoids. 相似文献
37.
A simple and practical procedure for the reduction of acetals to ethers is described. It is based on the use of a 1,1,3,3-tetramethyldisiloxane (TMDS)-Pd/C system in the presence of a Brønsted acid as the co-catalyst. The reaction occurs under mild conditions and ethers are obtained in high yields. 相似文献
38.
Brendan M. SmithAndrew E. Graham 《Tetrahedron letters》2011,52(47):6281-6283
Acyclic acetals and ketals undergo exchange reactions in the presence of catalytic quantities of indium(III) triflate and diols to generate the corresponding cyclic acetals and ketals in excellent yield. The protocol is rapid, employs mild conditions and can be adapted to employ solvent-free reaction conditions. We have further developed this methodology to encompass a tandem acetalisation-acetal exchange protocol which provides facile access to cyclic ketals from unreactive ketones also under very mild, solvent-free reaction conditions. 相似文献
39.
Catherine L. DaviesAnne-K. Duhme-Klair 《Tetrahedron letters》2011,52(35):4515-4517
The Tb(III)-complex of a cholesterol-DTPA conjugate was prepared in a one-step procedure from the tert-Butyl-protected form of the ligand through reaction with TbCl3.6H2O and NaI in refluxing acetonitrile. The acid-labile carbamate linker that connects the chelating DTPA moiety with the cholesterol unit of the ligand stays intact under these conditions. The combination of deprotection of the ligand with terbium complexation reduces the overall number of synthetic steps required and thus increases the efficiency and overall yield of the reaction sequence. 相似文献
40.
Vaishali R. Vohra Daniel F. Schmidt Christopher K. Ober Emmanuel P. Giannelis 《Journal of polymer science. Part A, Polymer chemistry》2003,41(24):3151-3159
The phenomenon of intercalation is widely known as a key process in the area of polymer/layered silicate nanocomposites. In the formation of such nanocomposites, a polymer chain is intercalated between the layers of a layered (silicate) host, typically giving a well-ordered multilayered stack with a repeat distance of only a few nanometers. Intercalated systems are excellent models for studies of confined geometries, and they often display enhanced material properties as well. In this study, we examined a series of polymers in which it was possible to reverse the intercalation process (i.e., to achieve deintercalation). Homopolymers and copolymers of poly(methyl methacrylate) and poly(tetrahydropyranyl methacrylate) (PTHPMA) were intercalated into an organically modified synthetic fluoromica. Thermally induced deprotection of the tetrahydropyranyl group resulted in the transformation of PTHPMA into poly(methacrylic acid), which was then observed to deintercalate from the silicate host. X-ray diffraction and thermogravimetric analysis were used to study the deintercalation process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3151–3159, 2003 相似文献