Methyl selective cleavage

Selective cleavage of an aiyl methylenedioxy group, or an aryl methyl ether, by boron trichloride has been investigated. 

Sodium ethanethiolate has been examined for the selective cleavage of aryl methyl ethers. Methyl ethers para to an electron-withdrawing group are cleaved preferentially. ... 

Watanabe, K. Noda, K., and Maruhashi, K., Selective cleavage of 10-methyl benzo b naphtho 2,1-d thiophene by recombinant Mycobacterium sp strain. Biotechnology, Letters, 2003. 25(10) pp. 797-803. 

Homoallyl ethers or sulfides.1 gem-Methoxy(phenylthio)alkanes (2), prepared by reaction of 1 with alkyl halides, react with allyltributyltin compounds in the presence of a Lewis acid to form either homoallyl methyl ethers or homoallyl phenyl sulfides. Use of BF3 etherate results in selective cleavage of the phenylthio group to provide homoallyl ethers, whereas TiCl effects cleavage of the methoxy group with formation of homoallyl sulfides. 

Selective cleavage of aryI methyl ethers.1 The sodium salt (NaH) of N-melhylaniline in the presence of HMPT cleaves methyl (and benzyl) aryl ethers in... 

The alternative selective cleavage of the allyl ester was achieved by Pd(0)-catalyzed allyl transfer. Because the Fmoc group is sensitive to morpholine, a very weak base must be used as the allyl-trapping nucleophile. IV-Methyl aniline was favorable, and its use as a scavenger nucleophile gave rise to the acid 29 in a high yield. 

Scheme 28 Selective Cleavage of a Phosphonate Methyl Ester with Bromotrimethylsilane 66 ...

Fuchigami and coworkers and Yoshida and coworkers independently found that anodic oxidation of benzylsilanes in the presence of nucleophiles such as alcohols and carboxylic acids resulted in a selective cleavage of the C—Si bond and the oxygen nucleophiles were introduced exclusively into the benzylic position (equation 6)11-13. In the absence of nucleophiles, the benzylsilane itself plays a role of a nucleophile and benzyl(trimethylsilyl-methyl)benzene is formed (equation 7)11,12. 

Reductive cleavage oflH-tMopyrane (l).4 T reatment of 1 with 2 equi v. of sodium in HMPT generates a dianion (a) by a selective cleavage of the S-vCH2 bond. Protonoloysis followed by methylation yields the pure (Z,Z)-diunsaturated methyl sulfide 2 with retention of configuration of the double bonds. 

Alternatively, a more nucleophilic anionic reagent can be generated by selective cleavage of a single trimethylsilyl group with methyl lithium-lithium bromide complex. This 1ithiobutadlyne derivative will react with electrophiles such as carbonyl compounds or primary alkyl iodides. 2... 

Selective hydrolysis can be used to remove the 0-6 protecting group of methyl 2,3,4,6-tetrakis-0-(trimethylsilyl)-a-D-glucopyranoside [403, 404]. Under properly controlled conditions, selective cleavage at one or both of the primary positions of pertrimethyl-silylated a,a-trehalose has been achieved [405]. The simple heteronuclear 1H29Si chemical shift correlated two-dimensional NMR spectroscopy enables the assignment of positions of trimethylsilyl substituents [406]. Interestingly, octakis-0-(tri-methylsilyl)sucrose is a stable, crystalline material which has been even proposed as an internal standard for GLC [407]. 

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