Microwave induced single step green synthesis of some novel 2-aryl aldehydes and their analogues

A microwave induced process for the synthesis of substituted 2-aryl aldehydes and analogues of general formula 1

• R′ is selected from the group consisting of CH3, C2H5, C6H5 and C6H4-(4-OCH3);
• X is O or N—NH—SO2—C6H4—CH3;
• R1 to R5 are selected from the group consisting of H, OH, OCH3, C6H5, and a halogen atom, or R2+R3 together represent a —(CH═CH—CH═CH)— group or a —(O—CH2—O)— group;
• comprising the steps of:
• a) reacting a substituted aryl alkene and an N-halosuccinimide and a phase transfer catalyst in a solvent under microwave irradiation to form a halohydrin which rearranges to a 2-aryl aldehyde in one pot without the formation of an intermediate epoxide;
• b) transferring the reaction mixture of step (a) into ice cold water and extracting with an organic solvent;
• c) washing the organic solution of step (b) with aqueous sodium thiosulphate, brine and water;
• d) drying the organic layer of step (c) over anhydrous sodium sulphate, filtering and evaporating to dryness to completely remove the solvent to obtain a residue;
• and
• e) purifying the residue of step (d) on silica gel to obtain the substituted 2-aryl aldehydes of general formula 1.