Butadienemonoxide reactswitbbighregioselectively withanhydridesto givepreferentially diestersof 2-buten-l,4-diolin presenceofpalladiumphosphinecomplexes. Reaction regioselectivityis shongly influencedby the nature of palladiumIigand,anhydrideand solvent. @ 1997Publishedby Elsevier Science Ltd.
Reactions of allylic epoxides with various nucleophiles catalyzed by palladium complexes via rr-allylpalladium intermediate are well known'-'. As shown in Scheme 1, the nucleophile NuH can attack the rc-allylcomplex to give two isomenc products 3 and 4:
4 With carbon nucleophiles, the attack takes place at the terminal position to give the 1,4 isomer, while when oxygen nucleophiles are used the addiction is scarcely selective, and the 1,2 isomer is preferred.
Only tnphenylsilanol reacts with vinyl epoxide', in presence of Pd complexes with bidentate ligrrnds, to give the 1,4 isomer.
In this paper we report a new method for the regioselective 1,4 functionalization of butadiene monoxide 1 by using carboxylic anhydrides.
We were interested in the synthesis of2-buten-1,4-diol from butadiene monoxide, as it is easily transformed into 1,4-butanediol, an important intermediate in the synthesis of polymers Since water is not a suitable nucleophile for the reaction with n-allyl palladium complex,' we moved toward different oxygen nucleophiles, such as carboxylates, which would also afford 2-buten-1,4-diol, after hydrolysis of the produced hydroxyesters. Actually