Synthesis of 4H-chromene derivatives

A method for preparing a 4H-chromene derivative of a formula:

• from a salicylaldehyde derivative of a formula:
• 3
• 4
• and an alkyl cyanoacetate of a formula:
• NC-CH2-COOR3
• wherein,
• R1 and R2 are selected from the group consisting of hydrogen, CH3, CH2CH3, CH2CH=CH2, CH2Br, CF3, NH2, OH, OCH3, CN, N02, Cl, Br, F, COOH or COOCH3;
• and R3 is selected from the group consisting of hydrogen, CH3, CH2CH3, CH2CH2CH3, CH2CH2CH2CH3, C(CH3)3, CH2Ph or CH2CH20CH3;
• comprising the steps of
• a) suspending said salicylaldehyde derivative in a first solvent;
• b) combining said salicylaldehyde derivative suspension with said alkyl cyanoacetate to form a first reaction mixture;
• c) adding a molecular sieve into said first reaction mixture to form a second reaction mixture;
• d) stirring said second reaction mixture at about 15-30° C for about 8- 20 hours;
• e) filtering off said molecular sieve;
• f) washing said filtered molecular sieve from step e) at least one time with a second solvent and collecting filtrates;
• g) removing said second solvent from said filtrates from step f) to form a residue;
• h) solidifying said residue;
• and
• i) crystallizing said solidified residue.