Bicyclobutanes and cyclobutenes: Unusual carbocyclic monomers

Hall, H. K.; Padías, Anne Buyle

doi:10.1002/pola.10618

Cited by 30 publications

(33 citation statements)

References 47 publications

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“…C Labeling Experiments to Explore C(sp 3 )−C(sp 3 ) Bond Formation. To determine whether reversible C(sp 3 )− C(sp 3 ) is occurring in the absence of added ligand, a 13 Clabeling experiment was conducted whereby a benzene-d 6 solution of ( Me PDI)Fe(s-trans-η 4 -C 4 H 6 ) was treated with 3 equiv of 13 C 2 H 4 . Oxidative cyclization quantitatively generated the S = 0, (PDI)Fe metallacycloheptene as judged by 1 H and 13 C{ 1 H} NMR spectroscopy (Scheme 8A).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…An excess of ethylene was used to suppress competing retro-[2 + 2] cyclization of the formed metallocycle that complicated interpretation of the spectroscopic data, and previous studies have shown that excess ethylene does not trigger vinylcyclobutane formation. 17 Examination of the metallocyclic product by 13 C NMR spectroscopy established incorporation of the isotopic label in three positions − α, β, and γ-carbons−of the metallocycle. This result is inconsistent with a static metallocycle, where oxidative cyclization between butadiene and ethylene would place the 13 C label exclusively at the α and β positions.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Catalyst Design Principles Enabling Intermolecular Alkene-Diene [2+2] Cycloaddition and Depolymerization Reactions

et al. 2021

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Aryl-substituted pyridine(diimine) iron complexes promote the catalytic [2 + 2] cycloadditions of alkenes and dienes to form vinylcyclobutanes as well as the oligomerization of butadiene to generate divinyl(oligocyclobutane), a microstructure of poly(butadiene) that is chemically recyclable. A systematic study on a series of iron butadiene complexes as well as their ruthenium congeners has provided insights into the essential features of the catalyst that promotes these cycloaddition reactions. Structural and computational studies on iron butadiene complexes identified that the structural rigidity of the tridentate pincer enables rare s-trans diene coordination. This geometry, in turn, promotes dissociation of one of the alkene arms of the diene, opening a coordination site for the incoming substrate to engage in oxidative cyclization. Studies on ruthenium congeners established that this step occurs without redox involvement of the pyridine(diimine) chelate. Cyclobutane formation occurs from a metallacyclic intermediate by reversible C(sp3)–C(sp3) reductive coupling. A series of labeling experiments with pyridine(diimine) iron and ruthenium complexes support the favorability of accessing the +3 oxidation state to trigger C(sp3)–C(sp3) reductive elimination, involving spin crossover from S = 0 to S = 1. The high density of states of iron and the redox-active pyridine(diimine) ligand facilitate this reactivity under thermal conditions. For the ruthenium congener, the pyridine(diimine) remains redox innocent and irradiation with blue light was required to promote the analogous reactivity. These structure–activity relationships highlight important design principles for the development of next generation catalysts for these cycloaddition reactions as well as the promotion of chemical recycling of cycloaddition polymers.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Catalyst Design Principles Enabling Intermolecular Alkene-Diene [2+2] Cycloaddition and Depolymerization Reactions

et al. 2021

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“…In most cases, polymerization of the BCB was observed. 15 At this stage, we decided to explore an alternative approach that would involve triplet energy transfer (Scheme 2B). In this scenario, the substituent bound to the BCB should be capable of being sensitized.…”

Section: Scheme 1 Cycloaddition Approaches Towards [211]-bicyclohexanesmentioning

confidence: 99%

Strain Release [2p+2s]-Cycloadditions for the Synthesis of [2.1.1]-Bicyclohexanes Initiated by Energy Transfer

Guo

Chang

Herter³

et al. 2022

Preprint

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Saturated bicycles are becoming ever more important in the design and development of new pharmaceuticals. In this manuscript, a new strategy for the synthesis of [2.1.1]-bicyclohexanes is described. These bicycles are significant as they have defined exit vectors, yet many substitution patterns are underexplored as building blocks. The process involves sensitization of a [1.1.0]-bicyclobutane followed by cycloaddition with an alkene. The scope and mechanistic details of the methods are discussed.

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“…The stereochemistry of ring-opening polymerizations of episulfides, lactones, lactides, N-carboxy-a-amino acid anhydrides, and other monomers has been studied but not as extensively as the epoxides [Boucard et al, 2001;Chatani et al, 1979;Duda and Penczek, 2001;Elias et al, 1975;Guerin et al, 1980;Hall and Padias, 2003;Imanishi and Hashimoto, 1979;Inoue, 1976;Ovitt and Coates, 2000;Spassky et al, 1978;Zhang et al, 1990].…”

Section: LVIIImentioning

confidence: 99%

Stereochemistry of Polymerization

Odian

2004

Principles of Polymerization

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Constitutional (formerly: structural) isomerism is encountered when polymers have the same overall chemical composition (i.e., same molecular formula) but differ in connectivitythe order in which the atoms are connected to each other. Polyacetaldehyde, poly(ethylene oxide), and poly(vinyl alcohol) are constitutional isomers. The first two polymers are CH CH 3 O C H 2 CH OH CH 2 CH 2 O n n Polyacetaldehyde Poly(ethylene oxide) Poly(vinyl alcohol) n obtained from isomeric monomers, acetaldehyde and ethylene oxide. The third is obtained by hydrolysis of poly(vinyl acetate) since vinyl alcohol does not exist (it is the enol form of acetaldehyde). Poly(methyl methacrylate) and poly(ethyl acrylate) are isomeric polymers CH 2 C CH 3 CO 2 CH 3 CH 2 CH CO 2 C 2 H 5 n n Poly (methyl methacrylate) Poly (ethyl acrylate) formed from isomeric monomers. Poly(E-caprolactam) and poly(hexamethylene adipamide) are isomeric even though the monomers are not isomeric. Similarly, the 1 : 1 copolymer of Principles of Polymerization, Fourth Edition.

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Bicyclobutanes and cyclobutenes: Unusual carbocyclic monomers

Cited by 30 publications

References 47 publications

Catalyst Design Principles Enabling Intermolecular Alkene-Diene [2+2] Cycloaddition and Depolymerization Reactions

Catalyst Design Principles Enabling Intermolecular Alkene-Diene [2+2] Cycloaddition and Depolymerization Reactions

Strain Release [2p+2s]-Cycloadditions for the Synthesis of [2.1.1]-Bicyclohexanes Initiated by Energy Transfer

Stereochemistry of Polymerization

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