title: Intramolecular cycloadditions of cyclobutadiene with dienes: experimental and computational studies of the competing (2 + 2) and (4 + 2) modes of reaction.
abstract: Highly functionalized, cyclobutene-containing adducts are afforded through intramolecular cycloadditions between cyclobutadiene and tethered dienes. The cycloaddition displays the following reactivity trend: cyclobutadiene serves as a dienophile in intramolecular reactions when it is connected to the diene through a four-atom tether. In cases where a three-atom linker separates the two reaction partners, the cyclobutadiene can function as both a diene and dienophile, affording a mixture of vinylcyclobutane (2 + 2) and cyclohexene-containing cycloadducts (4 + 2). Theoretical studies provide insight into the factors influencing the various pericyclic pathways operative in this system. In cases where cyclobutadiene functions as a diene to generate vinylcyclobutanes, these (2 + 2) adducts can be converted into the corresponding (4 + 2) cyclohexenyl products through a [3,3]-sigmatropic rearrangement.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: John
authors.initials: J
authors.lastname: Limanto
authors.forename: Kelli S
authors.initials: KS
authors.lastname: Khuong
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.forename: Marc L
authors.initials: ML
authors.lastname: Snapper
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis; D003503:Cyclobutanes / Q000737:chemistry*; D003516:Cycloparaffins / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry; D008958:Models, Molecular; D013816:Thermodynamics
chemical_list: D001643:Bridged Bicyclo Compounds; D003503:Cyclobutanes; D003516:Cycloparaffins; D004987:Ethers