Synlett 2013; 24(9): 1044-1060
DOI: 10.1055/s-0032-1316913
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© Georg Thieme Verlag Stuttgart · New York

From the Development of Catalysts for Alkyne and Alkyne–Nitrile [2+2+2] Cycloaddition Reactions to Their Use in Polymerization Reactions

Sentaro Okamoto*
Department of Material and Life Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, 221-8686, Japan   Fax: +81(45)4139770   Email: okamos10@kanagawa-u.ac.jp
,
Yu-ki Sugiyama
Department of Material and Life Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, 221-8686, Japan   Fax: +81(45)4139770   Email: okamos10@kanagawa-u.ac.jp
› Author Affiliations
Further Information

Publication History

Received: 07 February 2013

Accepted after revision: 18 March 2013

Publication Date:
12 April 2013 (online)


Abstract

Several systems consisting of a ligand, a metal compound, and zinc have been developed as catalysts for alkyne cycloaddition reactions and alkyne–nitrile co-cycloaddition reactions. N-Heterocyclic carbene (NHC)–iron(III) chloride–zinc, NHC–cobalt(II) chloride-zinc, and 2-{[(2,6-diisopropylphenyl)imino]methyl}pyridine (dipimp)–iron(III) chloride hexahydrate–zinc systems catalyzed intramolecular cyclotrimerization reactions of alkynes. The dipimp–cobalt(II) chloride hexahydrate–zinc system catalyzed cycloaddition reactions of a variety of alkynes in intramolecular, partially intramolecular, and fully intermolecular fashions. The ethane-1,2-diylbis(diphenylphosphine)–cobalt(II) chloride hexahydrate–zinc system was effective in catalyzing the [2 + 2 + 2] co-cycloaddition of diynes with nitriles. Nickel complexes with an ionic liquid-tagged ligand converted 1,6-diynes into the corresponding cyclooctatetraenes in a toluene–ionic liquid biphasic system in the presence of zinc. The dipimp–nickel(II) chloride hexahydrate–zinc catalyst polymerized 1,6-diynes to form conjugated polyene cyclic polymers. These results and their applications in synthesis, including controlled polymerization reactions, are described.

1 Introduction

2 Alkyne [2+2+2] Cycloaddition

2.1 Development of N-Heterocyclic Carbene–Cobalt or Iron Compound–Zinc Catalyst Systems

2.2 Development of 2-{[(2,6-Diisopropylphenyl)imino]methyl}pyridine–Cobalt or Iron Salt–Zinc Catalyst Systems

2.2.1 Development of 2-{[(2,6-Diisopropylphenyl)imino]methyl}pyridine–Iron Chloride–Zinc Catalyst Systems

2.2.2 Development of the 2-{[(2,6-Diisopropylphenyl)imino]methyl}pyridine–Iron Chloride Hexahydrate–Zinc Catalyst System

2.3 The 2-{[(2,6-Diisopropylphenyl)imino]methyl}pyridine–Cobalt(II) Chloride Hexahydrate–Zinc Catalyst System

2.3.1 Reactivity and Functional Group Compatibility

2.3.2 Catalyst Activation

3 Alkyne–Nitrile [2+2+2] Co-cycloaddition

4 Applications

4.1 Uses in Organic Synthesis

4.2 Use as a Method for Polymer Synthesis

4.2.1 Preparation of Diverse Polymerizable Molecules (a Monomer Library)

4.2.2 Use in Polymer Functionalization

4.2.3 Use as a Polymerization Reaction

5 Other Reactions

5.1 Nickel-Catalyzed [2+2+2+2] Cycloaddition and Cycloaddition Polymerization of 1,6-Diynes

5.2 Hydroalkynylation of Internal Alkynes

6 Conclusion