Acetals tritylation

In their behavior toward acids and bases, trityl ethers resemble the acetals, glycosides and orthoesters, being fairly stable in alkali, but easily split by acidic reagents. Thus, in cases where carbonyl compounds are used to protect pairs of hydroxyl groups by the formation of acetals, tritylation may often be used to protect suitably situated individual hydroxyl groups. 

The resulting macrocyclic ligand was then metallated with nickel(II) acetate. Hydride abstraction by the strongly electrophilic trityl cation and proton elimination resulted in the formation of carbon-carbon double bonds (T.J. Truex, 1972). 

Trityl Ethers. Treatment of sucrose with four molar equivalents of chlorotriphenylmethyl chloride (trityl chloride) in pyridine gives, after acetylation and chromatography, 6,1, 6 -tri-O-tritylsucrose [35674-14-7] and 6,6 -di-O-tritylsucrose [35674-15-8] in 50 and 30% yield, respectively (16). Conventional acetylation of 6,1, 6 -tri-O-tritylsucrose, followed by detritylation and concomitant C-4 to C-6 acetyl migration using aqueous acetic acid, yields a pentaacetate, which on chlorination using thionyl chloride in pyridine and deacetylation produces 4,l, 6 -trichloro-4,l, 6 -trideoxygalactosucrose [56038-13-2] (sucralose), alow calorie sweetener (17). 

Acetates. Because of the significant interest in selective acetylation reactions of sucrose, the need for a convenient and unambiguous method of identification has been recognized (34,35). The position of an acetyl group in a partially acetylated sucrose derivative can be ascertained by comparison of its H-nmr acetyl methyl proton resonances after per-deuterioacetylation with those of the assigned octaacetate spectmm. The synthesis of partially acetylated sucroses has generally been achieved either by way of selectively protected derivatives such as trityl ethers and cychc acetals or by direct selective acetylation and deacetylation reactions. 

A -Pyrazolines such as (410) are oxidized by iodine, mercury(II) acetate and trityl chloride to pyrazolium salts (411), and compound (410) even reduces silver nitrate to Ag° (69JOU1480). Electrochemical oxidation of l,3,5-triaryl-2-pyrazolines has been studied in detail (74BSF768, 79CHE115). They Undergo oxidative dimerization and subsequent transformation into the pyrazole derivative (412). 

Me3SiI, CH2CI2, 25°, 15 min, 85-95% yield.Under these cleavage conditions i,3-dithiolanes, alkyl and trimethylsilyl enol ethers, and enol acetates are stable. 1,3-Dioxolanes give complex mixtures. Alcohols, epoxides, trityl, r-butyl, and benzyl ethers and esters are reactive. Most other ethers and esters, amines, amides, ketones, olefins, acetylenes, and halides are expected to be stable. 

Trityl Chloride Imidazole Thiophosgene Hydrogen Sulfide Acetic Acid... 

The primary OH group can be selectively blocked by the bulky triphenyl-methyl (trityl) moiety, followed by esterification at the secondary OH groups and removal of the protecting trityl group. Thus 2,3-di-O-acetyl cellulose has been obtained by this procedure. Moreover, regioselectively substituted mixed cellulose esters, acetate/propionate, were prepared by subsequent acy-... 

Benzaldehyde can be condensed with the N-silylated urethane 671 and aUyltri-methylsilane 82 in the presence of trityl perchlorate to give, via an intermediate 0,N-acetal, the substituted urethane 672 in high yield [197]. 0,N-Acetals such as 673 condense with the enol silyl ether of acetophenone 653 in the presence of TMSOTf 20 to give the co-hydroxyurethane 674 in 94% yield [198] (Scheme 5.62). 

The unusual formation of an anhydro sugar by the hydrolysis of a trityl derivative has been described.76 The treatment of 5-trityl-D-ribofuranose triacetate with hydrogen bromide in acetic acid gives a ribosan diacetate which is presumed to be 1,5-anhydro-D-ribofuranose diacetate. 

A. Agarwal and Y. D. Vankar, Selective deprotection of terminal isopropylidene acetals and trityl ethers using HCIO4 supported on silica gel, Carbohydr. Res., 340 (2005) 1661-1667. 

On treatment with dimethyl sulfoxide-acetic anhydride followed by sequential oximation, reduction, detritylation, and acid hydrolysis, a tetra-(6-0-trityl)-cyclohexaamylose was reported to afford 2-amino-2-deoxy-D-glucose, in addition to D-glucose, indicating459 that... 

Starting with the same acetal (35), but proceeding by way of the diacetate 40, instead of the dibenzoate 36, it was possible to prepare,51 in high yield, the p-toluenesulfonate 41 by sequential trityla-tion and p-toluenesulfonylation. Compound 41 was then subjected to solvolysis in the presence of sodium acetate in moist N,N-dimethyl-formamide, and the product (42) was successively acetylated and de-tritylated to give 3,4,6-tri-0-acetyl-2,5-anhydro-D-allitol (43). The... 

Synthesis of 2,3,4,l, 3, 4, 6 -hepta-0-acetyl-6-0-tritylsucrose (9) has also been achieved by an unambiguous route.24 Treatment of 2,3,r,3, 4, 6 -hexa-0-acetyl-4,6-0-benzylidenesucrose25 (7) with aqueous acetic acid for 6 min at 100° gave 2,3,l, 3, 4, 6 -hexa-0-ace-tylsucrose (8) which, on tritylation with chlorotriphenylmethane in pyridine followed by conventional acetylation with acetic anhydride, afforded24 compound 9. 

Trityl ethers and acetals of sucrose have generally been used as precursors for the synthesis of partially acylated derivatives of sucrose. Deacetalation of 3,4,3, 4 -tetra-0-acetyl-2,l 6,6 -di-0-(diphenylsilyl)sucrose (33) and 3,3, 4, 6 -tetra-0-acetyl-2,l 4,6-di-0-isopropylidenesucrose (35) with aqueous acetic acid for 25 min at 50° gave 3,4,3, 4 -tetra-0-acetylsucrose27 (34) and 3,3, 4, 6 -tetra-0-ace-tylsucrose32 (36), respectively. Synthesis of 2,3,4,3, 4 -penta-0-acetyl-... 

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