New reaction of di- and trichloromethylbenzenes with orthoformic esters

Abstract

We have discovered a new reaction of di-and trichloromethylbenzenes I with orthoformic esters II and found that the product structure depends on the nature of X, temperature, and reagent ratio. Thus, at X = H and reagent ratio 1 : 2.2, the major reaction product after 39-h heating at 225oC is acetal V. Increasing the heating temperature to 237oC and changing the reagent ratio to 1 : 1 favors formation of aldehyde VI. At X = Cl, reagent ratios 1 : 1 and 1 : 3, temperature 180oC, and reaction time 10317 h, the major products are benzoic acid chloride VIII or ester IX. Irrespective of the nature of X, alkyl formate X and alkyl halide VII are also formed. PhCXCl 2 + HC(OR) 3 %$ PhCX(OR)Cl + HC(OR) 2 Cl, I II III IV IIIa + II %$ PhCH(OR) 2 + IV, V V + I %$ 2IIIa, IIIa %$ PhCHO + RCl, VI VII IIIb %$ PhCOCl + VII, VIII VIII + II %$ PhCOOR + IV, IX IV %$ HCOOR + VII, X I, III, X = H (a), Cl (b); I, III!V, VII, X, R = Me (a), Et (b); IX, R = Et.Compounds I exhibit a clearly pronounced electrophilic reactivity toward oxygen-containing organic compounds [1, 2]. As follows of the above data, benzotrichloride Ib is a stronger electron acceptor than benzylidene chloride Ia. We suggest that the reaction involves initial substitution of one chlorine atom in compounds I by an alkoxy group. The resulting a-chloroether IIIa further exchanges with ortho ester II to form acetal V. Similar conversion of achloroethers was previously described [3]. Under more rigid temperature conditions (237oC), acetal V acts as a dechloroalkoxylating agent toward benzylidene chloride Ia. When insufficient or no ortho ester II is present, compound IIIa undergoes thermal decomposition into benzaldehyde (VI) and alkyl chloride VII. a,a-Dichloroether IIIb is much more labile than a-chloroether IIIa and decomposes into alkyl halide VII and benzoyl chloride (VIII). The latter is alkoxylated with the ortho ester to give ethyl benzoate IX. Chloroacetal IV, too, is unstable and decomposes into alkyl formate X and compound VII [4].

Recent Developments in the Polychloroalkylation by Use of Simple Alkyl Chlorides

“…Alkyl chloride units, especially polychlorinated hydrocarbons, are a very important class of functional groups, which are widely found in bioactive molecules such as pharmaceuticals and pesticides [1] . Simultaneously, polychlorinated hydrocarbons units also can further transformed into a variety of new compounds, including aldehyde, [2a–d] ester, [2e–h] ketone, [2i–n] carboxylic acid, [2o–r] alkene, [2s–t] carbene, [2u–x] etc [2y–z] . Therefore, the formation of polychlorinated alkane units have been well established over the past few decades.…”