Trityl of alcohols

The tritylation of alcohols under neutral conditions has been achieved using p-methoxybenzyl trityl ether in the presence of DDQ. A selective cleavage of trityl ethers by CBr4-MeOH has been attributed to the formation of traces of HBr. Ceric ammonium nitrate on silica gel rapidly cleaves trityl and mono and di-methoxytrityl ethers whereas CeCb-Nal in refluxing acetonitrile effects the selective cleavage of trityl and dimethoxytrityl ethers under neutral conditions. ... 

Mild benzhydrylation (diphenylmethylation) of primary and secondary saccharide alcohols, and tritylation of the primary alcohols, were promoted by 4A AW-300 MS at room temperature through a dehydration mechanism in the absence of any strong protic or Lewis acid. While protection of a single primary or secondary hydroxyl... 

The tritylone group (22), which has been used199 for the protection of alcohols, resembles the trityl group, but it is more stable to acid. It... 

Only a few examples have been reported of the etherification of alcohols with resin-bound diarylmethyl alcohols (Entry 5, Table 3.30 Entry 5, Table 3.31 [564]). Diarylmethyl ethers do not seem to offer advantages over the more readily accessible trityl ethers, which are widely used as linkers for both phenols and aliphatic alcohols. Attachment of alcohols to trityl linkers is usually effected by treating trityl chloride resin or 2-chlorotrityl chloride resin with the alcohol in the presence of a base (phenols pyridine/THF, 50 °C [565] or DIPEA/DCM [566] aliphatic alcohols pyridine, 20-70 °C, 3 h-5 d [567-572] or collidine, Bu4NI, DCM, 20 °C, 65 h [81]). Aliphatic or aromatic alcohols can be attached as ethers to the same type of light-sensitive linker as used for carboxylic acids (Section 3.1.3). 

Polystyrene-bound allylic or benzylic alcohols react smoothly with hydrogen chloride or hydrogen bromide to yield the corresponding halides. The more stable the intermediate carbocation, the more easily the solvolysis will proceed. Alternatively, thionyl chloride can be used to convert benzyl alcohols into chlorides [7,25,26]. A milder alternative for preparing bromides or iodides, which is also suitable for non-benzylic alcohols, is the treatment of alcohols with phosphines and halogens or the preformed adducts thereof (Table 6.2, Experimental Procedure 6.1 [27-31]). Benzhy-dryl and trityl alcohols bound to cross-linked or non-cross-linked polystyrene are particularly prone to solvolysis, and can be converted into the corresponding chlorides by treatment with acetyl chloride in toluene or similar solvents (Table 6.2 [32-35]). 

Arnett and Hofelich measured heats of reaction of a variety of alcohols with SbF5/FS03H in sulfuryl chloride fluoride to form their respective carbocations at constant temperature (-40 °C). In this superacid medium there were no ion-pair complications126 and hence reliable calorimetric data were obtained for various cyclopropyl and phenyl substituted cations. The heats of reaction for the formation of tricyclopropylcarbinyl cation (-59.2 kcalmol ), trityl cation (-49.0 kcalmol1) and ferr-butyl cation (-35.5 kcalmol1) show that the relative order of the stabilization of the cationic center is cyclopropyl >... 

The employment of trityl trifluoroborate is particularly interesting. This reagent is able to introduce trityl groups on both primary and secondary alcohols54 and to selectively oxidize secondary trityl ethers to ketones in the presence of primary trityl ethers.55 Thus, treatment of diols with trityl trifluoroborate leads to tritylation of both alcohols followed by oxidation of the secondary trityl ether, resulting in the formation of a ketone possessing a trityl-protected primary alcohol. A work-up by mild acidic hydrolysis provides the deprotection of the primary trityl ether and formation of a hydroxy ketone.54... 

Trityl trifluoroborate produces the tritylation of both alcohols and the regioselective oxidation of the resulting secondary trityl ether. The primary trityl ether is hydrolyzed on contact with silica gel during the work-up, resulting in the formation of an 80% yield of the... 

In a typical experiment, trityl benzyl ether (5.0 mmole) is added to a stirred solution of the trityl salt (0.50 mmole) in acetonitrile. After4 hr., water is added and the products isolated, fienzaldehyde and triphenylmethane are obtained in quantitative yields. The reaction thus provides a method for oxidation of alcohols to aldehydes or ketones. 

Oxidation of benzyl ethers with trityl fluoroborate can be used either to prepare aromatic aldehydes or to cleave benzyl ethers of alcohols. 

Quantitative analysis is carried out in one of several ways depending on the solubility of the detritylated compound. If the latter is insoluble in an organic solvent which dissolves the trityl ether, a weighed sample of the ether (tritylcellulose, for example) is dissolved in a solvent such as chloroform, and a saturated solution of hydrogen chloride in chloroform is added. The solvent must be anhydrous and free of alcohol. The detritylated compoimd separates rapidly and is removed by filtration, washed with chloroform, dried and weighed. The combined chloroform solutions are then evaporated to dryness, and the weight of the trityl chloride residue is determined. 

Uchiro, Ft, Mukaiyama, T, Trityl salt catalyzed stereoselective glycosylation of alcohols with 1-hydroxyribofuranose, Chem. Lett., 79-80, 1996. 

Protection and deprotection oj 0-acetylation of alcohols and accu Trityl ethers are cleaved by ITV not affected. Discrimination of ary l (alkyl TBS ethers are selectively hy such amides by brief treatment witf Thioacetals are converted to car lodinations. In the preparat added. lodination of aromatic 1 -(tosyloxy)-1,2-benziodoxol-3( 1H iodination of 3,4-bis(trimethylsilyl i a combination of iodine and sih unsymmetrical 3,4-diarylthiophene a-Methoxy-a,P-unsaturated et (1 -methoxyalkylidene)-mngsten(O) the unsaturated esters. When iodim low. 

The reagent is used for the synthesis of phosphomonoesters of alcohols, particularly of nucleotides. It is coupled to the alcoholic component in pyridine using dicyclo hexylcarbodiimide (DCC) as condensing agent, as illustrated for the case of 5 -0-tritylthymidine. Acid hydrolysis eliminates the protective trityl group, and very mild... 

A 9-phenylfluoren-9-yl-based linker can also be used for the attachment of alcohols. This Hnker shows improved acid stability compared with the trityl Hnker. The Hnker has been appHed to the synthesis of a peptide alcohol [71]. 

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