Cobalt-catalyzed ring expansion/ring opening of oxetanes using phosphine oxides as promoters under hydroformylation conditions

Cobalt-catalysed hydroformylation of epoxides in the presence of phosphine oxides

“…38 The best results were obtained with tricyclohexylphosphine oxide P2 (Table 1, entry 7), which was the best promoter for the cobalt-catalysed ring expansion/ring opening of oxetanes, too. 35 Although the reaction in the presence P4 , a structurally more complex compound, showed similar results (Table 1, entry 9), we decided to choose P2 for further studies. It is worthwhile to highlight the lower performance of triphenylphosphine oxide P3 (Table 1, entry 8), claimed in the Shell patent as an efficient promoter for the cobalt catalysed hydroformylation of ethylene oxide under more severe conditions.…”

“…32 We have recently showed that phosphine oxides are able to efficiently promote some cobalt catalysed processes under mild conditions, such as the hydroformylation of olefins, 33 reductive etherification of benzaldehyde derivatives, 34 and ring expansion/ring opening of oxetanes. 35 Based on these works, herein, we report the results of the systematic evaluation of simple, relatively cheap, and commercially available phosphine oxides in the cobalt-catalysed hydroformylation of epoxides aiming to synthesize β-hydroxyaldehydes under mild conditions. The developed methodology for a model system was combined with the consecutive one-pot hydrogenation, which was then applied to produce 1,3-diols starting from epoxides (Fig.…”

Ring expansion/opening reactions of epoxy ene-amides: access to azabicyclononene, tetrahydropyridine and tetrazole scaffolds

“…Ring expansion reactions constitute an efficient atom economic strategy to construct medium to large-size cyclic cores from small cyclic molecules. 1 The relief of ring strain (26–28 kcal mol −1 ) in three-membered rings like aziridine, epoxide or cyclopropane is a useful asset that can be taken advantage of to expand the ring size to four and higher-membered ones. In particular, the ring expansion strategy for epoxide (oxirane) provides a straightforward platform for the construction of highly functionalized medium-sized ring structural frameworks (Scheme 1a–c).…”