Anisole cleavage

Picolyl ethers are prepared from their chlorides by a Williamson ether synthesis (68-83% yield). Some selectivity for primary versus secondary alcohols can be achieved (ratios = 4.3-4.6 1). They are cleaved electrolytically ( — 1.4 V, 0.5 M HBF4, MeOH, 70% yield). Since picolyl chlorides are unstable as the free base, they must be generated from the hydrochloride prior to use. These derivatives are relatively stable to acid (CF3CO2H, HF/anisole). Cleavage can also be effected by hydrogenolysis in acetic acid. ... 

Bis(tosyloxy)benzene derivatives may be selectively cleaved a tosyl group ortho or para to an electron-withdrawing group (e.g., an ester group) is cleaved preferentially to one in the meta position, whereas in derivatives of anisol, cleavage of the tosyl group meta to the methoxy group is preferred [252]. 

This was treated with thiocarbonyldiimidazole or oxalydiimidazole, followed by HF/ anisole cleavage from the resin, generating double heterocycle products 250 and 251, respectively. 

CF3COOH, anisole, CH2Cl2. Anisole is present to scavenge the diphenylmethyl cation liberated during the cleavage reaction. 

CF3CO2H, PhSCH3, 25°, 3 h. ° The use of dimethyl sulfide or anisole as a cation scavenger was not as effective because of side reactions. Benzyl ethers of serine and threonine were slowly cleaved (30% in 3 h complete cleavage in 30 h). The use of pentamethylbenzene had been shown to increase the rate of deprotection of 0-Bn-tyrosine. ... 

SiCl4, TFA, anisole. SiCl4 serves to reduce the sulfoxide prior to acid-catalyzed cleavage. Other sulfoxide reducing agents could probably be used. 

TFA, anisole, 75% yield. " Thioanisole has been used in this cleavage reaction to scavenge the benzyl cation7 Its absence results in considerable alkylation of the indolocarbazole nucleus7 ... 

This group was developed for the protection of primary amides of amino acids. It is introduced by amide bond formation with the benzhydrylamine. It is cleaved with 1 MSiCl4/anisole/TFA/0° or 1 MTMSOTf/thioanisole/TFA, 0°. Cleavage occurs by initial sulfoxide reduction followed by acidolysis. ... 

The exact time and temperature required for complete reaction must be determined for each individual compound. It has been observed that nucleophilic demethylation of methyl o-alkoxyaryl ethers is accelerated relative to anisole [Benzene, methoxy-],6 and this reaction is no exception. Lithium diphenylphosphide cleavage of anisole is complete in about 4 hours in refluxing tetrahydrofuran, whereas the present reaction is complete within 2 hours at 25°. 

If R is tertiary, RCOmay lose CO to give R, so that the alkylarene ArR is often a side product or even the main product. This kind of cleavage is much more likely with relatively unreactive substrates, where the acylium ion has time to break down. For example, pivaloyl chloride (McaCCOCl) gives the normal acyl product with anisole, but the alkyl product MesCPh with benzene. In the other mechanism an acyl cation is not involved, but the 1 1 complex attacks directly. 

In a pyrogram of Bisphenol A poly(formal) (6), the peak products are identified as a-methylstyrene, phenol, 4-hydroxy-a-methylstyrene, and isopropyl phenol by Py-GC/MS. These products are identical with the degradation products from Bisphenol A. In addition to the decomposition products of Bisphenol A, 4-isopropenyl anisole is also identified as a product. The pyrograms of Bisphenol AF poly(formal) (7) contain only two major species, pentafluoroisopropenyl benzene (product T) and pentafluoroisopropenyl anisole (product 2 ). They correspond to a-methylstyrene, 4-hydroxy-amethylstyrene from Bisphenol A poly(formal) (6) and are produced by the cleavage of phenylene-oxy bonds and oxy-methylene bonds according to (Scheme 6). 

The peptide was synthesized on TentaGel S RAM resin (lg, 0.25 mmol loading). Cleavage from the resin and deprotection was performed with TFA/H20/anisole/TIS (88.5 5 5 1.5, 20 mL) for 2 h at rt and the crude product was precipitated with tBuOMe/hexane (2 1) yield of crude product 160 mg. The relatively low yield (28%) is due to reattachment as determined by amino acids analysis of the resin hydrolysate (40% reattachment). The title compound was obtained by preparative HPLC (linear gradient of 0.1% aqTFA/0.08% TFAin MeCN from 90 10 to 40 60 in 105min) yield 40mg (10%) ESI-MS (m/z) Found 2543.2. Calcd for CjcBHisil bjCb Sej 2542.2. 

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