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Article

Pd²⁺-Catalyzed Cyclocopolymerization of 1,5-Hexadiene and CO: Regioselectivity of Olefin Insertion

Supporting Info

Samuel L. Borkowsky and Robert M. Waymouth*

Department of Chemistry, Stanford University, Stanford, California 94305

Macromolecules, 1996, 29 (20), pp 6377–6382

DOI: 10.1021/ma960319x

Publication Date (Web): September 23, 1996

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

Abstract

The cyclocopolymerization of 1,5-hexadiene and CO with Shell-type catalyst systems comprising palladium(II) complexes in the presence of chelating phosphines yields soluble cyclocopolymers containing 5- and 6-membered cyclic ketones. Cyclocopolymerization of 1,5-hexadiene and CO in the presence of Pd(OAc)₂, 1,3-bis(diphenylphosphino)propane (Dppp), 1,4-naphthaquinone, and Ni(ClO₄)₂·6H₂O in chloroform/methanol (100−20/1) afforded a soluble cyclocopolymer 2 containing both 5- and 6-membered ring ketones in the polymer backbone. Cyclocopolymerization under similar conditions in the presence of 1,3-bis(diisopropylphosphino)propane (Dipp) gave a soluble cyclocopolymer 3 containing only 6-membered rings. Epimerization of the 6-membered ring cyclocopolymer 3 with 4-(dimethylamino)pyridine provided evidence for an initial prevailingly cis microstructure (ca. 3/1 cis/trans) for the 2,5-disubstituted cyclohexanone repeating units of the cyclocopolymer. The regioselectivity for insertion of 1,5-hexadiene into the Pd−acyl bonds was inferred from the nature of the ring formed in the cyclocopolymerization. The formation of 5-membered cyclopentanone repeating units was interpreted as a signature for an initial 2,1-insertion of 1,5-hexadiene; the formation of 6-membered cyclohexananone rings was interpreted in terms of an initial 1,2-insertion of the 1,5-hexadiene.

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