Polyoxometalates: Powerful Catalysts for Atom‐Efficient Cyclopropanations

Abstract

Abstract:The polyoxometalate-based catalytic cyclopropanation of olefins by ethyl diazoacetate (EDA) is reported. The outstanding catalyst productivity (TONs up to 100,000) and the use of equimolar EDA/olefin ratio confer to the methodology a high sustainability. Preliminary mechanistic investigations are also discussed.

Thiosemicarbazone copper complexes as competent catalysts for olefin cyclopropanations

“…Even if a poor diastereoselection was observed, to the best of our knowledge, this is the higher TON reported for a single site copper catalyst in homogeneous catalytic cyclopropanation [23]. A TON of 100,000 has been recently reported by us with a dinuclear copper polyoxometalate catalyst [26].…”

“…Rarely metal complexes can give high selectivities in cyclopropanation reactions together with high turnover number (TON) [26]. In this work, different ligands have been synthesized and characterized, by changing the steric and electronic properties of the starting aldehyde employed in the condensation reaction.…”

Highly diastereoselective cyclopropanation of α-methylstyrene catalysed by a C2-symmetrical chiral iron porphyrin complex

“…It should be noted that a catalyst loading of 0.005% (TON of 2 Â 10 4 , Table 2, entry 9) is one of the lowest observed for cyclopropanations 39,40 and, to the best of our knowledge, leads to the highest reported TON for metallo porphyrin-based catalysts. To achieve the best catalyst loading/reaction time relationship, 0.01% of 2Fe was employed to better investigate the effect of the temperature on the enantioselectivity.…”

Cyclopropanation Reactions Mediated by Group 9 Metal Porphyrin Complexes

“…The catalytic activity of several cobalt complexes of modified Schiff bases, [63][64][65] terpyridines, [66] nitrogen macrocycles, [67] pincer ligands [68] and polyoxometallates [69] was also reported. However, porphyrin ligands represent, along with Schiff bases, the most frequently used class of ligands to synthesise cobalt cyclopropanation catalysts.…”