Esters, xanthate structures

Another method that provides chlorides from alcohols with retention of configuration involves conversion to a xanthate ester, followed by reaction with sulfuryl chloride. This method is thought to involve collapse of a chlorinated adduct of the xanthate ester. The reaction is useful for secondary alcohols, including stoically hindered structures.8... 

II. STRUCTURES OF XANTHATE ANIONS, ESTERS, AND OXIDATION PRODUCTS... 

Three more crystal structures are included in this section for the sake of completeness. The molecular structure of the only crystallographically determined structure of a xanthate ester is shown in Fig. 5 (25). In fact, this is a diester in that two isobutylxanthates are connected via an ethylene bridge. 

In this book, he emphasized the importance of the microscopic and the submicroscopic structure of fibrous high polymers. The reactions of cellulose with water, aqueous alkalis, organic bases, ammonia, and strong salt solutions were all stressed. Special attention was given to various types of cellulose esters, to cellulose xanthate, and to the cellulose ethers. The oxidation of cellulose under a variety of conditions was described, as were the hydrolysis reactions. The latter included discussions on reversion and on the kinetics of acid hydrolysis. It is interesting to note that Heuser, who earlier had criticized the terms hydrocellulose and oxycellulose, and had... 

Xanthate zan- that (1831) n. A sodium salt of a dithiocarbonic acid ester, in particular the one formed in the viscose-rayon process by the reaction between sodium hydroxide cellulose and carbon disulfide and having the structure shown below, called cellulose xanthate or viscose. The viscose is subsequently precipitated, filtered, extruded as... 

Xanthate n zan- that n (1831) A sodium salt of a dithiocarbonic acid ester, in particular the one formed in the viscose-rayon process by the reaction between sodium hydroxide cellulose and carbon disulfide and having the structure shown below, called cellulose xanthate or viscose. The viscose is subsequently precipitated, filtered, extruded as filaments into dilute sulfuric acid, washed, and dried to make viscose that be spun into Rayon fabric, and extruded thin sheets are called Cellophane . (Kadolph SJJ, Langford AL (2001) Textiles. Pearson Education, New York Ash M, Ash I (1982-1983) Encyclopedia of Plastics, Polymers, and Resins, Vols. I-in. Chemical Publishing, New York). 

Next, alcohol 35 was transformed into 36 by reductive dehydroxylation via the nonisolated intermediate xanthate. Hydrolysis of the ester group in 35 to form 30 was followed by decarboxylation to generate 37 by using an improved Barton s method employed with HOTT (5-(l-oxido-2-pyr-idinyl) 1,1,3,3-tetramethylthiouronium hexafluorophos-phate) [35]. Treatment of 37 with TBAF furnished alcohol, which was converted into the proposed structure of paesslerin A by using scandium-catalyzed acetylation. Unfortunately, comparisons of the H- and C-NMR data of the synthetic compound with those reported for the natural product revealed that the substances are not identical. The 2D-NMR data for synthetic 29 are fiiUy consistent with the structure of the target. The result clearly demonstrates that a revision of the structure of natural paesslerin A is required (Scheme 4.17). 

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