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Abstract Low‐strain cyclic olefin monomers, including five‐membered, six‐membered, eight‐membered, and macrocyclic rings, have been recently exploited for the synthesis of depolymerizable polyolefins via ring‐opening metathesis polymerization (ROMP). Such polyolefins can undergo ring‐closing metathesis depolymerization (RCMD) to regenerate their original monomers. Nevertheless, the depolymerization behavior of polyolefins prepared by ROMP of seven‐membered cyclic olefins, an important class of low‐strain rings, still remains unexplored. In this study, we demonstrate the chemical recycling of polyheptenamers to cycloheptene under standard RCMD conditions. Highly efficient depolymerization of polyheptenamer was enabled by Grubbs' second‐generation catalyst in toluene. It was observed that the monomer yields increased when the depolymerization temperature increased and the starting polymer concentration was reduced. A near‐quantitative monomer regeneration (>96%) was achieved within 1 h under dilute conditions (20 mM of olefins) at 60°C. Moreover, polyheptenamer exhibited a decomposition temperature above 430°C, highlighting its potential as a new class of thermally stable and chemically recyclable polymer materials.
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Ring Expansion via One-Pot Conversion of Lactone Acetals to Cyclic Enones. Synthesis of (±)-1- epi -Xerantholide
Baeyer-Villiger oxidation of alpha-alkoxy ketones 1 provides lactone acetals 2, which react with the lithium salts of di-methyl(alkyl) phosphonates in the presence of LaCl3•2LiCl to provide cyclic enones 3 in good to excellent yields after treatment with dilute aqueous potassium carbonate. Thus, five-, six-, and seven-membered lactones are con-verted to five-, six-, and seven membered cyclic enones. The utility of this two-step ring expansion method is demonstrated in the synthesis of (±)-1-epi-xerantholide from 5-methyl-2-cyclohexen-1-one.
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- Award ID(s):
- 2003261
- PAR ID:
- 10630099
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Organic Letters
- Volume:
- 26
- Issue:
- 41
- ISSN:
- 1523-7060
- Page Range / eLocation ID:
- 8691 to 8695
- Subject(s) / Keyword(s):
- Total Synthesis Organic Chemistry Ring Expansion Medium-ring Synthesis
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.orglett.4c02855
