Trityl methyl ether

Trialkylsilyl enolates can be oxidized to the corresponding a, S-nnsatnrated ketones with trityl tetrafluoborate or trityl methyl ether in the presence of BFsOEta. It has been observed that the use of trityl cations often leaves snbstantial amonnts of saturated ketones. The amonnt of these species can be rednced by the nse of ddq as in the case of... 

Triphenylmethanol is a tertiary alcohol and undergoes, as expected, SnI reactions. The intermediate cation, however, is stable enough to be seen in sulfuric acid solution as a red-brown to yellow solution. Upon dissolution in concentrated sulfuric acid, the hydroxyl is protonated then the portion is lost as HjO (which is itself protonated) leaving the carbocation. The bisulfate ion is a very weak nucleophile and does not compete with methanol in the formation of the product, trityl methyl ether. 

Triphenylmethyl methyl ether Trityl methyl ether... 

FIG. 1 H nmr spectrum of triphenylmethyl methyl ether (trityl methyl ether) (250 MHz). 

Ozonolysis of 6 to produce 7 was studied at temperatures ranging from -78 to -0 °C in mixtures of dichloromethane and methanol. The intermediates that formed were found to be stable below -30 °C. Diol 7 was obtained in high yields when the reaction mixture was quenched with aqueous sodium borohydride. If the reaction mixture was warmed to room temperature before the quench, a complex mixture of products formed as indicated by the NMR spectrum. Similarly, only polymeric products were formed when the ozonolysis was carried out without methanol even at -78 °C. When ozonolysis was done at -5 to 0 °C in the presence of methanol, formation of trityl methyl ether was noticed, a result similar to which has been observed before [2], Diol 7 was obtained in near quantitative crude yield when ozonolysis was carried out below -30 °C, followed by the addition of the reaction mixture to cold, aqueous sodium borohydride solution. The product was used without further purification in the next step. 

The other way to generate thioesters at the penultimate step of penem synthesis is acylation of silver thiolates 226. These compounds are conveniently obtained by cleavage of the corresponding trityl sulfides 225 with silver nitrate and methanol [51a, 144] trityl methyl ether and nitric acid (trapped by pyridine or, better, imidazole) are liberated in the process. Tetrahydropyranylthioethers 227 [145] and acetyl thioesters 228 [51a, 52] were also reported to be cleavable to the corresponding argentiothio-phosphoranes of general formula 226. 

Ethers are among the most used protective groups in organic synthesis. They vary from the simplest, most robust, methyl ether to the more elaborate, substituted, trityl ethers developed for use in nucleotide synthesis. They are formed and removed under a wide variety of conditions. Some of the ethers that have been used to protect alcohols are included in Reactivity Chart 1. ... 

The use of iodotrimethylsilane for this purpose provides an effective alternative to known methods. Thus the reaction of primary and secondary methyl ethers with iodotrimethylsilane in chloroform or acetonitrile at 25—60° for 2—64 hours affords the corresponding trimethylsilyl ethers in high yield. The alcohols may be liberated from the trimethylsilyl ethers by methanolysis. The mechanism of the ether cleavage is presumed to involve initial formation of a trimethylsilyl oxonium ion which is converted to the silyl ether by nucleophilic attack of iodide at the methyl group. tert-Butyl, trityl, and benzyl ethers of primary and secondary alcohols are rapidly converted to trimethylsilyl ethers by the action of iodotrimethylsilane, probably via heterolysis of silyl oxonium ion intermediates. The cleavage of aryl methyl ethers to aryl trimethylsilyl ethers may also be effected more slowly by reaction with iodotrimethylsilane at 25—50° in chloroform or sulfolane for 12-125 hours, with iodotrimethylsilane at 100—110° in the absence of solvent, " and with iodotrimethylsilane generated in situ from iodine and trimcthylphenylsilane at 100°. ... 

Homoallyl methyl ethers.4 Trityl perchlorate catalyzes a reaction of allyltri-methylsilanes with dimethyl acetals or ketals to form homoallyl methyl ethers in 60-90% yield. Diphenylboryl triflate is a somewhat less efficient catalyst. Example ... 

Boc,245 /-butyl ester,246 trityl ether247 and even tris(p-methoxyphenyl)methyl ether.248 The oxidation-sensitive PMB normally resists the action of PCC,249 as well as the sulfur-containing protecting groups dithioacetals250 and mono-thioacetals.251... 

Ohio1 8 reported some acetyl and tosyl esters, as well as some ethers, from 1,2- and 2,3-isopropylidene-L-sorbose, and simultaneously Khouvine and Valentin147 studied the acetylation of tritylated methyl a-L-sorbo-pyranoside. The methyl l-trityl-3,4,5-triacetyl-a-L-sorbopyranoside which they obtained was detritylated to methyl 3,4,5-triacetyl-a-L-sorbo-pyranoside. A crystalline tritrityl-diacetyl-L-sorbose148 has also been reported. 

O-AJkylation of stannylene derivatives of 1,2-diols can be used to introduce members of the trityl ether family onto a secondary alcohol — an otherwise difficult task. In the example shown in Scheme 4.212, a very labile bis- 4-meth-oxyphenyl)(phenyl)methyl ether was installed on a Shikimic Acid derivative.400... 

In this manner 6-methyl-D-glucopyranose (XXIX) and some of its derivatives were synthesized from n-glucose derivatives containing a free hydroxyl group only in the 6-position. The 6-methyl ethers of D-mannose and of methyl a-n-mannoside were obtained similarly. Haworth and coworkers synthesized 2,3,4-trimethyl-n-glucose from 6-trityl-D-glucose and used the ether for the elucidation of structural problems. 

The stability of ethers and mixed acetals as protecting groups for alcohols varies from the very stable methyl ether to the highly acid-labile trityl ether. However, all ethers are stable to basic reaction conditions. Hence, ether or mixed acetal protecting groups specifically tolerate... 

In the course of the synthesis of 2-amino-2-deoxy-3,4-di-0-methyl-D-glucose, the 3-methyl ether of methyl 2-acetamido-2-deoxy-6-0-trityl-a-D-glucopyranoside was obtained as a secondary product on methylation with Purdie s reagents. Elimination of the trityl group afforded the same glycoside as that obtained by Neuberger. 

A 4-methyl ether of a 2-amino-2-deoxy-D-glucose derivative was first obtained as a by-product in the methylation of methyl 2-acetamido-2-deoxy-6-O-trityl-a-n-glucopyranoside with Purdie s reagents. ... 

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