Ethoxalyl ketones

Ethoxalyl ketones [after citation of ref. 3]. The direct monomethylation of A4-cholestenone gives 4-methylcho estenone-3-one. Monomethylation at C2 can be achieved by prior condensation at C2 with diethyl oxalate to give the 2-ethoxy-oxalate (2).3a This group evidently stabilizes an enolate anion from (2) favorable for... 

The same one-carbon unit has been employed in a convenient isoflavone synthesis from deoxybenzoins (76S326). Other methods of ring closure of phenyl benzyl ketones to this heterocycle have been reviewed (B-62MI22400) and include triethyl orthoformate (56PIA(A)(44)36), zinc cyanide (58CB2858), ethyl formate (80BCJ831) and ethoxalyl chloride (70JCS(C)1219). 

---