Heterogenized homogeneous catalysts. Hydrogenation of methyl sorbate by polystyrene-anchored tricarbonylchromium

Abstract

The reaction of a swollen 1% divinylbenzene cross-linked polystyrene with hexacarbonylchromium gave polymer-anchored tricarbonylchromium moieties 6 bonded to the polymer's phenyl rings. Using this heterogenized catalyst, methyl sórbate was converted selectively (96-97%) to (Z)-methyl 3-hexenoate with small amounts of methyl hexanoate and (-E)-methyl 2-hexenoate in cyclohexane at 160°and 500 psi of hydrogen. The product distribution was sensitive to solvent and reaction temperature. No significant hydrogenation of cyclohexene or (£,£,£)-!,5,9-cyclododecatriene occurred at 150°and 500 psi of hydrogen in 24 hr. This heterogenized homogeneous catalyst system is discussed in relation to known homogeneous hydrogenation catalysts for methyl sórbate.

cis‐bond‐producing hydrogenation of polyunsaturates catalyzed by polymer‐complexed Cr(CO)3 catalysts

“…This so-called anchored Cr(CO)a catalyst was as selective for the hydrogenation of methyl sorbate to 3-hexenoate as the homogeneous arene-Cr(CO)3 complex catalysts (7,8). Pittman et al (6) confirmed our previous observations (7,8) that on the basis of infrared the 3-hexenoate product has a cis configuration. Although the activity of the "heterogenized" catalyst was poor (total conversion required >10 hr), it could be recycled.…”

“…Airlessware glassware (Kontes Glass Co., Vineland, NJ) and Oxy-Traps (AUtech Associates, Inc., Arlington Heights, IL) were employed to provide an oxygen-free N 2 atmosphere. The procedure of Pittman et al (6) was followed exactly to prepare a polystyrene-complexed Cr(CO) a as a reference catalyst equivalent to theirs. A mixture of sublimed Cr(CO) 6 and polystyrene beads cross-linked with 1% divinylbenzene in 1,2-dimethoxyethane is refluxed 48 hr under N2 in a Strohmeier reactor.…”

“…Recently, Pittman et al (6) reported a "heterogenized" chromium carbonyl catalyst prepared from styrene-divinylbenzene (1%) copolymer complexed with Cr(CO) 6. This so-called anchored Cr(CO)a catalyst was as selective for the hydrogenation of methyl sorbate to 3-hexenoate as the homogeneous arene-Cr(CO)3 complex catalysts (7,8).…”

Hydrogenation

“…The Crt COh moiety T/6 -bonded to the phenyl rings of polystyrene gives a selective catalyst for the hydrogenation of methyl sorbate to Z-methyl-3-hexenoate with 96-97% selectivity (reaction (5» [56]. …”

Polymer‐based catalysts for toluene hydrogenation

“…[1][2][3][4][5][6][7] As result of this process, the active site is bound to a heterogeneous surface. The main drawbacks of the use of this type of catalyst are related to the complexity of the (1) synthesis of the organometallic complex (2) synthesis of the functional polymer, and (3) attachment chemistry.…”