Single step green process for the preparation of substituted cinnamic esters with trans-selectivity

A single pot process for the preparation of substituted cinnamic esters with trans-selectivity of Formula I, excluding the toxic and hazardous cyanides as an oxidizing agent:

• wherein:
• each of X1, X2, X3, X4 and X5 is independently selected from the group consisting of hydrogen atom, an alkoxy group having 1 to 3 carbon atoms, a halide, a sulfide group, a haloalkyl group having 1 to 3 carbon atoms, an amino group, and cyano group;
• and
• R is selected from the group consisting of an alkyl, an aryl, an arylalkyl and an cycloalkyl group having carbon chain from 1 to 20 with or without substitutions at the aromatic ring, the process comprising the steps of:
• a) reacting cinnamaldehydes or cinnamyl alcohols of Formula II,
• wherein:
• R′ is selected from CHO and CH2OH;
• and
• each of X1, X2, X3, X4 and X5 is independently selected from the group consisting of hydrogen atom, an alkoxy group having 1 to 3 carbon atoms, a halide, a sulfide group, a haloalkyl group having 1 to 3 carbon atoms, an amino group, and cyano group,
• with an oxidizing agent, a catalyst, and an alcohol, optionally in the presence of an organic solvent, while stirring at room temperature, or refluxing, or under microwave irradiation or ultrasound for a period of time between about 1 minute and about 20 hours, to obtain substituted cinnamic esters of Formula I with trans-selectivity with a yield up to 98% in a single step;
• b) filtering the reaction mixture obtained in step (a) and collecting the filtrate;
• c) concentrating the filtrate obtained in step (b) or directly passing the same through a column of solid adsorbent selected from the group consisting of alumina and silica gel;
• and
• d) eluting the packed column of step (c) with solvents of different polarities, to obtain the substituted cinnamic esters of Formula I with trans-selectivity free from side products.