22610-15-7Relevant academic research and scientific papers
Lewis and Br?nsted basicity of phosphine-diazomethane derivatives
Schneider, Carolin,LaFortune, James H.W.,Melen, Rebecca L.,Stephan, Douglas W.
supporting information, p. 12742 - 12749 (2018/09/27)
The compounds EtOC(O)CHNNPR3 (R = Ph 1, Cy 2, tBu 3) were prepared via the reactions of the diazomethane and a phosphine. In subsequent reactions with B(C6F5)3, the compounds 2 and 3 are shown to exhibit Lewis b
Triphenylphosphane-modified cobalt catalysts for the selective carbonylation of ethyl diazoacetate
Ungvari, Neszta,Foerdos, Eszter,Balogh, Janos,Kegl, Tamas,Parkanyi, Laszlo,Ungvary, Ferenc
experimental part, p. 3837 - 3851 (2010/12/24)
The triphenylphosphane-substituted carbonyl cobalt complexes Co 2(CO)7(PPh3), Co2(CO) 6(CHCO2Et)(PPh3), and [Co(CO) 3(PPh3)2][Co(CO)4] were found to be more effective precatalysts in the carbonylation of ethyl diazoacetate under atmospheric pressure of carbon monoxide at 10 °C in dichloromethane solution than the parent Co2(CO)8 and Co2(CO) 7(CHCO2Et) complexes. The highly reactive (ethoxycarbonyl)ketene is the primary product of the catalytic carbonylation, which dimerizes in the absence of a proper scavenger. In the presence of ethanol as the trapping reagent diethyl malonate is the final product of the carbonylation reaction. The formation of (ethoxycarbonyl)ketene using the catalyst precursor Co2(CO)7(PPh3) occurs in a catalytic cycle, where Co2(CO)6(PPh3) and Co2(CO)6(CHCO2Et)(PPh3) are the repeating species. The 16e species Co2(CO)6(PPh 3) is involved in the deazotization of ethyl diazoacetate, and Co2(CO)6(CHCO2Et)(PPh3) leads to the (ethoxycarbonyl)ketene formation. In the absence of carbon monoxide or at low CO concentration the reaction of Co2(CO)6(CHCO 2Et)(PPh3) with ethyl diazoacetate is the source of Co2(CO)5(CHCO2Et)2(PPh3), which is not an active catalyst for the carbonylation of ethyl diazoacetate. Using [Co(CO)3(PPh3)2][Co(CO)4] as the catalyst precursor, the intermediary formation of [Co(CO) 3(PPh3)2][Co(CO)3(O=C=CHCO 2Et)] through radical pairs is assumed. Substituting PPh3 in Co2(CO)7(PPh3), Co2(CO) 6(CHCO2Et)(PPh3), and [Co(CO) 3(PPh3)2][Co(CO)4] by polymer-bound PPh3 results in active and reusable catalysts for the selective carbonylation of ethyl diazoacetate in dichloromethane solution at 40 °C and 11 bar of pressure with up to 5.1 mol of product/((mol of catalyst) h) turnover frequency.
Oxorhenium complexes as aldehyde-olefination catalysts
Santos, Ana M.,Pedro, Filipe M.,Yogalekar, Ameya A.,Lucas, Isabel S.,Romao, Carlos C.,Kuehn, Fritz E.
, p. 6313 - 6321 (2007/10/03)
Several oxorhenium compounds in the formal oxidation states V and VII are examined as catalysts for the aldehyde-olefination starting from diazo compounds, phosphines, and aldehydes. Of these, [ReMeO2(η 2-alkyne)] complexes provide the simplest catalysts to study, although [ReOCl3(PPh3)2] still remains the most efficient rhenium catalyst for aldehydeolefination described to date. Prior to the reaction with the Re catalysts the phosphine and the diazo compound react to form a phosphazine. No catalytic reaction occurs in cases where no phosphazine formation is observed. The first step of the catalytic cycle involves the formation of a carbene intermediate by the reaction of phosphazine and catalyst under extrusion of phosphine oxide and dinitrogen. In a second step the carbene reacts with aldehyde under olefin formation and catalyst regeneration. Excess of alkyne as well as the presence of ketones slows down the catalytic reaction. The olefination of 4-nitrobenzaldehyde with diazomalonate is possible with these Re catalysts. In contrast, this reaction does not take place either in the classical Wittig fashion from Ph3P=C(CO2Et)2 and aldehyde or by use of all other catalysts for aldehyde olefination reactions reported to date. Catalytic ylide formation from diazo compounds seems therefore not to be the only pathway through which catalytic aldehyde-olefination reactions can proceed.
