3 ,5 -Dimethoxybenzoin derivatives

Importantly, TV-carbamoyl derivatives of primary amines obtained from photolabile benzoins exist in varying proportions as cyclic hydroxyoxazolidinone tautomers. Therefore, the preparation of TV-carbamoyl derivatives of benzoins is applicable only for secondary amines and TV-alkylated amino acids. 244 At basic pH unsymmetrical benzoins, such as 3,5-dimethoxybenzoin, their mixed carbonate and carbamate derivatives, tend to equilibrate to the isomeric forms. Nevertheless, in TFA and aqueous solutions at pH 8 the structural integrity is fully maintained. 244 Preparation of 3,5-dimethoxybenzoin-derived carbamates of secondary amines and amino acids can be mediated by either CDI/methyl triflate in ni-tromethane 246 or 4-nitrophenyl chloroformate/DMAP in dry THF. 244 ... 

Dimethoxybenzoin Derivative, 980 4-Hydroxyphenacyl, 981 4-Methoxyphenacyl, 981 l-(2-Nitrophenyl)ethyl, 981 o-Nitrobenzyl, 981... 

A few years later, Sheets suggested that co-oxidation of the biimidazole derived from 2-chloro-3, 4 -dimethoxybenzoin and o-chlorobenzaldehyde and 2-(o-chlorophenyl)-4,5-diphenylimidazole would give a still less expensive photo-oxidant (Scheme 4.13) with less visible sensitivity, thus making for better photofixing. 

Pirrung, M.C. and Huang, F C.-Y.D (1995) Photochemical deprotection of 3, 5 -dimethoxybenzoin (DMB) carbamates derived from secondary amines. Tetrahedron Letters, 36, 5883—5884. 

Scheme 13 Photocyclization of Dimethoxybenzoin Carbamate Derivatives and Structure of the Inert Cyclic Carbamate...

Destrade and coworkers [150] have prepared a series of benzotrisfuran derivatives that give discotic mesophases. The synthesis, outlined in Scheme 37, hinges on the condensation of phloroglucinol with /j,p-dimethoxybenzoin to give hexakisfme-thoxyphenyl)benzotrisfuran. This intermediate is demethylated with pyridinium hydrochloride, and the resultant hexaphenol is acylated by treatment with an acid chloride... 

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