Tetrahydrofuran → Dicyclohexylcarbodiimide

Participants

Reaction Steps

Malonitrile is alkylated (or dialkylated) by treatment with NaH in an appropriate solvent such as dimethylformamide or tetrahydrofuran at 0° to 25° C. to give compounds (51). Treatment of the substituted nitrile with (n-Bu)3SnN3 in refluxing dioxane for 24 hours gives, after acidic hydrolysis, the tetrazole (52), which is then alkylated with an alkyl halide (R4Br) in CH3CN employing Et3N as base to give a mixture of regioisomers (53) and (54). The regioisomers are then separated by flash chromatography and each nitrile is then reduced to the corresponding aldehydes (55) and (56) by treatment with Raney nickel in formic acid at 60° C. The resulting aldehydes are then treated with a stabilized ylide such as ethyl (triphenylphosphoranylidene)acetate in CH2Cl2 at room temperature to give (57) and (58) which are reduced catalytically using hydrogen gas, Pd/C as catalyst in methanol or ethanol at room temperature to give esters (59) and (60). These are then hydrolyzed to the corresponding acids (61) and (62) by treatment with alcoholic (MeOH/EtOH) alkali metal hydroxide (NaOH or KOH) at reflux. The acids are then coupled with an appropriate amine employing carbonyldiimidazole in tetrahydrofuran at room temperature or dicyclohexylcarbodiimide in CH2Cl2 at 0° C. to give amides (63) and (64).

Provenance & Evidence