Vanadium catalysts alkane carboxylation

Alkanes also undergo carboxylation with CO, as shown in Scheme 2. Carboxylation of alkanes to carboxylic acids is one of the interesting and important functionalization processes. The first example of carboxylation of alkanes was performed on cyclohexane using a Pd(0Ac)2/K2S208/TFA catalyst system [2]. This carboxylation reaction was extended to gaseous alkanes, for example methane, ethane, and propane. Thus, acetic acid (AcOH) was synthesized from methane and CO in the presence of a Pd catalyst but with a low conversion yield [3]. Recently, the acetic acid synthesis was much improved by using vanadium catalysts such as VO(acac)2 and afforded AcOH almost quantitatively [4],... 

Scheme 2.9 Alkane carboxylation with CO and K2S2O8, in TFA (a) General reaction [13, 17, 54-62] and (b) proposed mechanism for an oxo-vanadium catalyst [54, 55],...

The thermally induced carboxylation of alkanes has been thoroughly investigated by the same group, who have developed a range catalysts, based on vanadium (VO(acac)2) or palladium analogs.22,22a,22b Photochemically induced carbonylation of linear alkanes, to afford aldehydes, is also known (Equation (15)).23,23a... 

Hiatt et a/.34a-d studied the decomposition of solutions of tert-butyl hydroperoxide in chlorobenzene at 25°C in the presence of catalytic amounts of cobalt, iron, cerium, vanadium, and lead complexes. The time required for complete decomposition of the hydroperoxide varied from a few minutes for cobalt carboxylates to several days for lead naphthenate. The products consisted of approximately 86% tert-butyl alcohol, 12% di-fe/T-butyl peroxide, and 93% oxygen, and were independent of the catalysts. A radical-induced chain decomposition of the usual type,135 initiated by a redox decomposition of the hydroperoxide, was postulated to explain these results. When reactions were carried out in alkane solvents (RH), shorter kinetic chain lengths and lower yields of oxygen and di-te/T-butyl peroxide were observed due to competing hydrogen transfer of rm-butoxy radicals with the solvent. 

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