Suzuki-Miyaura cross-coupling of potassium alkoxyethyltrifluoroborates: access to aryl/heteroarylethyloxy motifs.

The introduction of an alkoxyethyl moiety onto aromatic substructures has remained a long-standing challenge for synthetic organic chemists. The main reasons are the inherent instability of alkoxyethylmetallic species and the lack of general procedures to access them. A new method utilizing a cross-coupling strategy based on the exceptional properties of organotrifluoroborates has been developed, and the method allows an easy and efficient installation of this unit on a broad range of aryl and heteroaryl bromides.

Synthesis and reactivity of solid-supported organotrifluoroborates in Suzuki cross-coupling.

Solid-supported organotrifluoroborates were prepared in high yields by ion exchange with Amberlyst resins. The reactivity of solid supported aryltrifluoroborates was evaluated in Suzuki-Miyaura couplings with numerous aryl bromide partners. Electron-rich and -poor substituents were tolerated on both substrates, providing yields up to 90%. Examples of alkyl-, alkenyl-, alkynyl-, and heteroaryltrifluoborates were also successfully cross-coupled to aryl halides.

Suzuki coupling of potassium cyclopropyl- and alkoxymethyltrifluoroborates with benzyl chlorides.

Efficient Csp(3)-Csp(3) Suzuki couplings have been developed with both potassium cyclopropyl- and alkoxymethyltrifluoroborates. Moderate to good yields have been achieved in the cross-coupling of potassium cyclopropyltrifluoroborate with benzyl chlorides possessing electron-donating or electron-withdrawing substituents. Benzyl chloride was also successfully cross-coupled to potassium alkoxymethyltrifluoroborates derived from primary, secondary, and tertiary alcohols.

Direct alkylation of heteroaryls using potassium alkyl- and alkoxymethyltrifluoroborates.

A direct alkylation of various heteroaryls using stoichiometric potassium alkyl- and alkoxymethyltrifluoroborates has been developed. This method leads to the synthesis of complex substituted heterocycles, which have been obtained with yields up to 89%.

Synthetic approaches to amino analogues of N-acetylcolchinol.

A straightforward synthesis of aminodibenzoxepines, new analogues of N-acetylcolchinol, is reported by using two different strategies. The first strategy involves a Grignard addition, a biaryl Suzuki-Miyaura coupling, and a HF-mediated cyclodehydration as key steps. A second strategy, better adapted to the synthesis of analogues bearing a benzylic substituent, was designed by inverting the order of the Grignard addition and the biaryl coupling. This allowed the rapid and reliable production of a series of substituted aminodibenzoxepines. A chelate model was proposed to account for the diastereoselectivity observed in the Grignard addition step.