1 -Methoxy-3-trimethylsilyloxybuta-1,3-diene

IPreparation of l-methoxy-3-trimethylsilyloxybuta-l, 3-diene (Danishefsky s Idiene) and Diels-Alder addition with maleic anhydride. 

Under Lewis acid catalysis, l-methoxy-3-trimethylsilyloxybuta-1,3-dienes react with aldehydes to give dihydropyrones (Equation Si3.14). 

Diels-Alder Cycloadditions.—The range of functionalized diene systems, displaying regioselective behaviour in the Diels-Alder reaction, continues to expand. Notable new additions include l-phenylseleno-2-trimethylsilyloxy-4-methoxybuta-l,3-diene (82) and the isomers 1- and 2-methyl-l,3-bis(trimethylsilyloxy)buta-l,3-dienes (84) and (85). The diene (82) is readily derived from l-methoxy-3-trimethylsilyloxybuta-1,3-diene (81) and provides a direct route to the synthetically valuable 4-acylcyclohexa-2,5-dienones (83), whereas dienes (84) and (85) react with activated dienophiles (e.g. RCH=CHC02Et) in good yield, leading to keto-esters of the type (86) on hydrolysis. 

Cyclic Ketones.—Danishefsky has surveyed the Diels-Alder cycloaddition reactions of l-methoxy-3-trimethylsilyloxybuta-1,3-diene (76) (and its derivatives), which is available by enol silylation of the corresponding vinylogous ester [equation (41)]. These dienes react with a broad range of dienophiles to... 

---