New insights into the alkoxycarbonylation of propargyl alcohol

Abstract

The challenging carbonylation of propargyl alcohol is effectively catalyzed by Pd(OAc)2 in combination with diphenyl-(6-methyl-pyridin-2-yl)phosphine and methanesulfonic acid. In dichloroethane at 20–50 ◦C, the reaction affords with almost complete regioselectivity alkyl 2-(hydroxymethyl)acrylates. Turnover frequency numbers (TOF) of up to 450 h−1 can be achieved working at 50 ◦C, while a maximum turnover number (TON) of about 730 is obtained at 30 ◦C. The catalyst longevity is limited because the carbonylation product reacts with the phosphorus atom of the ligand to give a quaternary phosphonium\ud salt. This reaction leads to deactivation of the catalyst and eventually to palladium black formation

The intriguing methoxycarbonylation of trimethylsilylacetylene in the presence of Drent's catalytic system

“…In initial experiments (Scheme 3 and Table 1), the methoxycarbonylation of trimethylsilylacetylene was carried out in the presence of the catalytic system Pd(OAc) 2 / CH 3 SO 3 H/PyPPh 2 . The adopted reaction conditions were those usually employed with Drent's catalyst [9,10,12,24] that imply the use of an excess of the phosphine, reaction temperature in the 50 C to 80 C range, P(CO) in the 10to 50-atm range.…”

“…[9,10] When applied to terminal alkynes (see Scheme 1), the process usually proceeds with high regioselectivity (e.g., >95%) towards the branched product allowing to obtain in one step 2-substituted-α,β-unsaturated carboxylic esters that are key intermediates in industrial [11] and fine chemistry. [12,13] Works by Drent other researchers and us [8][9][10][11][13][14][15][16][17][18][19] showed that the presence of the 2-pyridyl group in the phosphino ligand plays a crucial role, because when such type of group is not present, the efficiency of the catalytic system is by far lower.…”

“…[ 9,10 ] When applied to terminal alkynes (see Scheme 1), the process usually proceeds with high regioselectivity (e.g., >95%) towards the branched product allowing to obtain in one step 2‐substituted‐α,β‐unsaturated carboxylic esters that are key intermediates in industrial [ 11 ] and fine chemistry. [ 12,13 ]…”

Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts

“…To study the activity of M(0)NPs-CS and optimize hydrogenation reaction conditions, preliminary experiments were carried out using (E)-cinnamaldehyde (I) as a model substrate and relevant data are reported in Table 1. As previously mentioned, the hydrogenation of (I) is challenging due to the possible formation of several by-products [44,[80][81][82][83][84][85] and is often chosen as model reaction considering both its scientific and industrial relevance [84][85][86][87].…”

Mechanistic Investigation on the Polymerization of Phenylacetylene by 2-Diphenylphosphinopyridine Rhodium(I) Catalysts: Understanding the Role of the Cocatalyst and Alkynyl Intermediates

“…24 The chelate bidentate coordination of the Ph 2 PPy ligand gives rise to a relative strained four-membered metallacycle which stabilizes some crucial intermediates in several processes catalyzed by the system Pd(OAc) 2 /PPh 2 Py/H + such as the methoxycarbonylation of propyne, 25 the hydrocarboxylation of acetylene 26 or the alkoxycarbonylation of alkynols. 27 However, the key of the high efficiency of these catalytic systems is likely the active role of the ligand as a "proton messenger" (P-N/P-NH + ) promoting fundamental steps of the catalytic cycle.…”