Synthesis of (E)-1-Aryl Alk-1-en-3-ones by Tetraphosphine/Palladium-Catalysed Heck Reactions of Alk-1-en-3-ones with Aryl Bromides

Abstract

The tetraphosphine cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane in combination with [Pd(C 3 H 5 )Cl] 2 affords a very efficient catalyst for the Heck reaction of alk-1-en-3-ones with aryl bromides. If appropriate reaction conditions are used (NaOAc as base, hydroquinone as stabilising agent and DMF as solvent) high yields of (E)-1-aryl alk-1-en-3-one derivatives are obtained. In general, higher reaction rates were observed with electron-poor aryl bromides, but the electron-rich aryl bromides 4-N,N-dimethylaminobromobenzene and 4-bromoanisole also led to the arylated enones. Even with sterically very congested aryl bromides such as 9-bromoanthracene, 2,4,6-trimethylbromo-benzene or 2,4,6-triisopropylbromobenzene, the expected (E)-1-aryl alk-1-en-3-ones were obtained in moderate to good yields. Moreover, several reactions can be performed with as little as 0.1% catalyst.