Pyranosyl chlorides

In fact, these reactions likely involve 13-dioxocarbenium ions, which can also be prepared from pyranosyl chloride and reduced to acetals thus endo- and exo-1,2-0-ethylidene-a-D-allapyranoses have been prepared from penta-O-acetyl-p-D-allopyranosyl chloride (reaction with sodium borohydride) [88]. These types of 1,2-acetoxonium ions ate also known to react with dialkylcadmium to give 1,3-diacetals [89]. 

Reduction of pyranosyl chlorides to glycals (10, 240).1 Reduction of the pyranosyl chloride 2 with lithium-ammonia results in a modest yield of the expected glycal 3 (8, 282-283) and the tetrahydropyran 4 in a 1 1 ratio. This reduction was... 

The Solvolysis of the Alpha- and Beta-3,4,6-Tri-O-acetyl-D-gluco-pyranosyl Chlorides, R. U. Lemieux and G. Huber, Can. J. Chem., 33... 

C12H17CIO7 3,4,6-Tri-0-acetyl-2-deoxy-D-gluco-pyranosyl chloride 66... 

Let us now come back to equation (1). So far we have used it to calculate 35ci NQR frequencies from the computed 3pz orbital populations of two simplified models. Then we compared the calculated figures with the observed resonances of the more complicated pyranosyl chlorides. Conversely, we may start from these observed resonances, and use formula (1) to derive experimental values of the 3pz orbital populations of pyranosyl chlorides, so as to gain direct insight into their electronic structure. If no double bonding is involved, and if a constant value of 2 is adopted bor b9 we can accept as an experimental observation that on all pyranosyl chlorides examined, the 3pz orbital population on axial chlorine is higher than the 3pz orbital population on equatorial chlorine by an amount of about 5% (up to 7% in the case of mannose).Some people may consider that a statement in terms of ionicity i is more suggestive. Equation (1) may be written ... 

Starting from pentoses and hexoses having varied conformations, we can prepare two collections of pyranosyl chlorides, with axial or equatorial chlorine atoms, the analogues of 2.25 and 2.26, respectively. As with 2-chlorooxane, the axial orientation of the chlorine in 2.25 corresponds to the stable conformation of methyl chloromethyl ether. A comparison of the geometrical data in solid state, when available, shows that the axial carbon-chlorine bond is invariably longer than the same bond in an equatorial position. Finally, Fig. 2.6 shows that, according to quadrupolar resonance spectroscopy, these compounds are divided into two groups. 

Helferich and Muller121,122 prepared a-D-glucopyranosides, including some disaccharides, by the reaction of 3,4,6-tri-O-acetyl-jS-D-gluco-pyranosyl chloride with alcohols in the presence of mercury(II) succinate. 

Complimentary to the use of pyranosyl chlorides as substrates for reductive lithiations is the use of pyranosyl phenylsulfones. These species are... 

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