Some conversions of allenyl ethers

Metallation of methoxypropadiene, CH 2 = C = CHOCH 3 , with butyllithium in ether, followed by reaction with carbonyl compounds, R 1 R 2 C = O (R 1 and R 2 = H or alkyl or R 1 R 2 C = cyclohexyl), affords carbinols, CH 2 = C = C[CR 1 R 2 (OH)]OCH 3 , in excellent yields. Acid‐catalysed hydrolysis of these carbinols gives nearly quantitative yields of unsaturated ketols, magnified image 1‐Methoxy‐1‐methylthiopropadiene, CH 2 = C = C(OCH 3 ) (SCH 3 ) (VI), has been obtained in 75% yield by adding CH 3 SSCH 3 to the lithiated allenyl ether. Acid‐catalysed addition of alcohols, ROH (R = CH 3 or C 2 H 5 ), to methoxypropadiene affords acrolein acetals, CH 2 = CHCH(OCH 3 ) (OR) (VII), in good yields. Diels‐Alder addition of ethoxypropadiene to a ,β‐unsaturated aldehydes, R 3 CH = CH ‐ CH = O (R 3 = H or CH 3 ), leads to derivatives of 2,3‐dihydropyran (VIII). The yields are moderate. magnified image