1,3- and 1,2-Unsaturated Derivatives as Valuable Synthetic Tools in Organometallic Syntheses

Annamaria      Deagostino; Cristina      Prandi; Silvia      Tabasso; Paolo      Venturello

Abstract

This review gives an overview of our recent developments in the chemistry of 1,3- and 1,2-butadiene derivatives, with a special attention to their use in palladium catalyzed reactions. The reactions of α,β-unsaturated and propargylic acetals with various lithium and mixed lithium-potassium Schlosser reagents will be firstly reviewed. These processes have afforded (E)-1-alkoxy-1,3-dienes, and (E)-1,3-enynes, 1,3-diynes or allenes, respectively. When the reactions have been carried out in the presence of suitable electrophiles a linear route to functionalized derivatives has been set up. The above-mentioned compounds can be thus considered valuable synthetic tools for the construction of various and more complex structures and, in particular, they have been established to be useful reagents for the Suzuki-Miyaura cross-coupling reaction. As a matter of fact, alkoxy-functionalized butadienylboronic esters have been synthesized, cross-coupled with both N-protected and N-unprotected haloanilines (or halophenols), and finally transformed under mild conditions into quinolines and quinolinones (or chromenes and chromenones). The second part of the paper will deal with our recent interest in the Heck coupling of conjugate systems. In particular, the synthesis of γ-arylated α,β-unsaturated carbonyl compounds, by regioselective Heck process on 1-alkoxy-1,3-dienes in ionic liquids will be reviewed, in conjunction with the Heck coupling of 1,2-dien-1-ols to α-arylated α,β-unsaturated aldehydes. A survey of the recent literature on closely related topics will complete the contribution.

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