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11.
The preparation of eighteen epoxy diazomethyl ketones 1 is described. Two general methods were developed. Firstly, treatment of the mixed anhydrides of glycidic acids and carbonic acid ester with diazomethane led to the title compounds in yields ranging from 17–74%. Secondly, glycidyl chlorides which were obtained from sodium glycidates and oxalyl chloride, gave the desired products upon treatment with diazomethane (yields 60–74%). The required α,β-epoxy carboxylic esters were prepared by Darzens condensation and epoxidation of α,β-unsaturated esters, but in some cases also by reaction of α-oxo carboxylic esters with diazomethane. 相似文献
12.
G. H. L. Nefkens B. Zwanenburg 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Trialkylalkynylborates are coordinatively saturated anionic species that through an intramolecular transfer mechanism behave like vinyl carbanions in reaction with electrophiles. 相似文献
13.
Acidolytic cleavage of unsymmetrically substituted dithioacetal monoxides, ArCH(SR)S(O)Me has been used to prepare linear unsymmetrical disulfides RSSMe. Disproportionation was suppressed by the addition of a small amount of benzyl mercaptan. The required starting materials were conveniently obtained from appropriately substituted sulfines ArC(=SO)SR and methyl lithium. The following disulfides were prepared: R =n-C4H9 (73.5%), n-C7H15 (78%), Ph (77.3%), AcO(CH2)10 (81.5%).The unsymmetrical dithioacetal PhCH(SEt)SC7H15-n gave upon oxidation with one equivalent of peracid a mixture of two dithioacetal monoxides which on treatment with HClO4 led to three disulfides. This result is discussed in term of the mechanism of acidolysis. 相似文献
14.
15.
G. Admiraal J. M. M. Smits Paul T. Beurskens F. M. C. Leemhuis L. Thijs B. Zwanenburg 《Journal of chemical crystallography》1996,26(4):305-308
The stereogeometry and absolute configuration of the title compound has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, P21,a=7.7976(2),b=7.8288(2),c=8.9791(4) Å, =90.331(4)o, Z=2. The crystal structure has been solved by vector search methods and refined toR=0.042 for 1798 observed reflections. 相似文献
16.
The synthesis of the C14-C23 macrocyclic subunit of cytochalasin B from pulegone is described. The key feature of this synthesis is the photo-induced rearrangement of epoxy diazomethyl ketone E to a γ-hydroxy alkenoic ester (Scheme 2). The intermediate epoxy alcohol F was prepared using the asymmetric Sharpless epoxidation. Considerable attention was given to the preparation of allylic alcohol 14, having a t-butyldimethylsilyloxy protecting function, as starting material for the asymmetric epoxidation, however, several unforeseen difficulties were encountered (Schemes 3 and 4). Satisfactory results were obtained using the methoxy group as protecting function (Scheme 5). The allylic alcohol 22 was prepared from bromide 20 by chain lengthening with propargyl alcohol. The Sharpless epoxidation of 22 took place with high induction. Conversion to epoxy ester 24, to diazo ketone 25 and photo-rearrangement to 26 and deprotection to give 28, completes the sequence. 相似文献
17.
The cyclo-addition reaction of diazomethane with α,β-unsaturated sulfones is described. Divinyl sulfone and phenyl vinyl sulfone give 1- or 2-pyrazolines depending on the reaction conditions. cis- and trans-1,2-Bis(methylsulfonyl)ethene form pyrazolines, which on reaction with either triethylamine or excess of diazomethane lead to substituted pyrazoles. 相似文献
18.
19.
Molecular mechanics (MM2) calculations on the conceivable seco-cage structures by homoketonization of two types of bridgehead substituted 1,3-bishomocubyl acetates, viz. type A : 4-acetoxy-pentacyclo[5.3.0.02,5.03,9.04,8] decan-6-one and its ethylene ketal, and type B: 8-acetoxypentacyclo [5.3.0.02,5.03,9.04,8]decan-6-one, its ethylene ketal and 8-acetoxypentacyclo[5.3.0.02,5.03,9.04,8]decane were performed. 相似文献
20.
New resolving bases for ibuprofen and mandelic acid: qualification by binary phase diagrams 总被引:1,自引:0,他引:1
Eelco J. Ebbers Bart J.M. Plum Gerry J.A. Ariaans Bernard Kaptein Quirinus B. Broxterman Alle Bruggink Binne Zwanenburg 《Tetrahedron: Asymmetry》1997,8(24):331-4057
New resolving bases for ibuprofen 1 and mandelic acid 2 were studied and qualified by their binary phase diagrams of the corresponding salts. It was shown that analysis of the binary phase diagrams gives a good prediction for a resolution process. A comparison of resolving bases revealed that (S)-phenylglycinol (S)-7 is the best resolving base for ibuprofen 1. By the same procedure, various resolving bases for mandelic acid 2 were studied. The known resolving base (S)-MBA 9 was found to be the best for this acid. 相似文献