Isopropyl methyl ether, synthesis

In fact, the reaction of alkoxides with alkyl halides or alkyl sulfates is an important general method for the preparation of ethers, and is known as the Williamson synthesis. Complications can occur because the increase of nucleo-philicity associated with the conversion of an alcohol to an alkoxide ion always is accompanied by an even greater increase in eliminating power by the E2 mechanism. The reaction of an alkyl halide with alkoxide then may be one of elimination rather than substitution, depending on the temperature, the structure of the halide, and the alkoxide (Section 8-8). For example, if we wish to prepare isopropyl methyl ether, better yields would be obtained if we were to... 

Trichloroalane in dichloromethane cleaves isopropyl aryl ethers leaving methyl aryl ethers intact. A variety of functional groups (aryl halides, 1,1-dihaloalkenes, aldehydes and acetates) withstand the reaction conditions but alkynes and TIPS ethers do not survive. Scheme 4 110 illustrates an application of the reaction to a synthesis of the Fagaronine alkaloids,201 TVichloroborane in dichloromethane may also be used for the deprotection of isopropyl ethers.202... 

Studies aimed at the synthesis of the tetracyclic steroid skeleton from dehydro-abietic acid have centred, in their initial stages, on transformations of the C-13 isopropyl group. The full paper describing the conversion of methyl 12-acetyl-abieta-8,ll,13-trien-18-oate into methyl 13-hydroxypodocarpa-8,ll,13-trien-18-oate by nitrodeacylation and dealkylation reactions, has appeared. Birch reduction of the methyl ether of the phenol afforded the a/5-unsaturated ketone (56) which is a useful synthetic intermediate. Methods for the conversion of podocarpic acid into the a) -unsaturated ketones (57 R = CO2H and CHjOAc) have been investigated reduction of the ester (58 R = C02Me) with lithium in liquid ammonia, which was accompanied by decarboxylation, gave only a... 

Classic examples of synthetic polymers exhibiting an aqueous LCST include poly-diethyl acrylamide), poly(dimethylaminoethyl methacrylate), poly(A -acryloylpyrrolidine), poly(2-isopropyl-2-oxazoline), elastin-like artificial polypeptides, poly(vinyl methyl ether) and poly(7V-isopropylacrylamide) (PNIPAM, Scheme 1). The latter has been by far the most studied and applied thermoresponsive polymer and therefore can be considered as the gold standard in this field of research. During the last decades, several thousands of research articles and patents described the synthesis, the properties and the applications of this fascinating macromolecule. 

Ether cleavage and further functionalization afforded the intermediate 268. The [5+2]-cycloaddition provided the hydroazulene 267 with the correct relative configuration at and C. Tracing back the synthesis of the pyryli-um ylide 266 leads to the astonishing realization that 2-methyl cyclopent-2-enone (90) was the original cyclic starting material and that the methyl as well as the isopropyl group were introduced by a sequence of cuprate addition and enolate alkylation (see Schemes 15, 31 and 36 for comparison). 

The simultaneous and selective protection of the two equatorial hydroxyl groups in methyl dihydroquinate [11L1, Scheme 3.111 j as the butane-2,3-diace-tal 111 2 was a key strategic feature in a synthesis of inhibitors of 3-dehydroqui-nate synthase.205 Later in the synthesis, deprotection of intermediate 111.4 required three steps (a) hydrolysis of the trimethylsilyl ether and the butane-2,3-diacetal with trifluoroacetic acid (b) cleavage of the isopropyl phosphonate with bromotrimethylsilane and (c) hydrolysis of the methyl ester with aqueous sodium hydroxide. Compound 111 1 has also been used in the synthesis of inhibitors 3-dehydroquinate dehydratase206 and influenza neuraminadase207-208 as well as shikimic add derivatives.209 210... 

This reaction is similar to the Williamson synthesis of ethers (method 115). Otthofotmates in which the alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and isoamyl have been prepared from chloroform. The yield of ethyl orthoformate is 45%. Mixed esters are obtained from a mixture of sodium alkoxides and chloroform. Benzotrichloride, C,HjCClj, is converted to methyl orthobenzoate in 86% yield by sodium methoxide in methanol, ... 

An aq. soln. of thiourea dioxide and NaOH added to a stirred mixture of methyl phenyl N-tosylsulfilimine, hexadecyltributylphosphonium bromide as phase transfer catalyst, and isopropyl ether, then stirred 4 hrs. at 70° -> methyl phenyl sulfide. Y 93%. F. e., sdso mercaptans from disulfides (cf. Synth. Meth. 14, 63), s. G. Borgogno, S. Colonna, and R. Fomasier, Synthesis 1975, 529 formulas s. Synth. Meth. 30, 700. 

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