Polymer‐supported phosphines: Reactivity of pendant and crosslink groups

Abstract

Two groups of phosphine‐containing resins were prepared by bead copolymerization. In one the phosphine residues were introduced as pendant groups with p‐styryldiphenylphosphine, whereas in the other the phosphine residues were located specifically at crosslinked points with bis(p‐styryl)phenylphosphine. Both groups of resins were used to convert alcohols to alkyl chlorides in the presence of carbon tetrachloride and benzaldyhyde to benzal chloride and β,β‐dichlorostyrene. In the first reaction an increase in the crosslink ratio of the support reduced the reactivity of the resins, although both octanol and octadecanol substrates behaved similarly. No clear difference emerged between resins with pendant phosphine groups and those located on crosslinks and the absence of a strong substrate size effect or substrate selectivity with both series of resins was apparent. The production of benzal chloride and β,β‐dichlorostyrene requires interaction of two phosphine residues to generate the reactive intermediate, and inhibition of phosphine–phosphine interactions in these highly crosslinked networks does indeed inhibit this reaction. Again both series of resins behaved similarly. Among the possible routes by which PPh3/CCl4 converts alcohols to chlorides one involving phosphine‐phosphine interactions must also be inhibited in these supported systems.

Polymer‐supported reagents, catalysts, and sorbents: Evolution and exploitation—A personalized view

“…With regard to the application of supported reactive species in chemistry, we have contributed in terms of polymeric reagents (phosphines,39, 71 peracids,72 and chiral borohydride73) and polymer‐supported chiral74 and achiral75 phase‐transfer catalysts and, perhaps most importantly of all, in the area of polymer‐supported transition‐metal complex catalysts, notably supported Pd(II),76 Mo (VI),77 V(V),78 Ti (IV),79 Mn (III),80 Pt(O),81 and Pd(O)82 species. Reactions and processes of interest have varied from commodity chemicals76, 77 to fine chemicals, the latter involving primarily asymmetric catalytic systems 79, 80.…”

Threefold Cross‐Linked Polystyrene–Triphenylphosphane Hybrids: Mono‐P‐Ligating Behavior and Catalytic Applications for Aryl Chloride Cross‐Coupling and C(sp3)H Borylation

“…Thus, using the PS backbone for designing phosphane ligands to favor a specific structure desirable for an increase in catalytic activity is difficult.Herein we report a new type of polystyrene-phosphane covalently bound hybrid, which was prepared through radical emulsion polymerization of styrenes in the presence of tris(pvinylphenyl)phosphane as a threefold cross-linker. [3][4][5] Our scenario is as follows: The threefold cross-linking increases the density of the polymer chain around the Ph 3 P core, and thus limits multidentae P-coordination to the metal, but the steric demand in proximity to the P atom is only moderate (Ph 3 P-like) owing to the spacer effect of the three aromatic rings on the P atom, which projects toward trigonal pyramid directions; consequently, the resulting mono-P-ligated metal system allows effective access of substrates for catalysis. In fact, this simple technique yielded novel immobilized monodentate tertiary phosphane ligands that specifically formed mono-ligated transition-metal complexes (Figure 2).…”

Synthesis of Acid Halides, Anhydrides and Related Compounds

“…22 The process has also been tried successfully for the conversion of alcohols to alkyl chlorides. There are, however, limitations in the fact that the starting material cannot be regenerated for the reaction with carbon tetrachloride.…”

“…Insertion of carbon monoxide and reductive elimination of an acid halide will complete the catalytic cycle. In this way it was shown that allyl chloride yields butenoic acid chloride in >80% yield according to equation (22).7 7 ,78 As well as palladium, rhodium and iridium also act catalytically.2 It is of no surprise that allylic halides, benzylic halides and aryl halides in particular are readily converted to acid halides. Simple aliphatic halides undergo the oxidative addition step more slowly and, if they carry hydrogen atoms on an sp3 hybridized C atom in the (3-position to the halogen atom, may give alkenes via (3-hydrogen elimination.…”