Intramolecular cycloadditions of cyclobutadiene with dienes: experimental and computational studies of the competing (2 + 2) and (4 + 2) modes of reaction.
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.
Limanto
John
J
Department of Chemistry, Merkert Chemistry Center, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, USA.
Khuong
Kelli S
KS
Houk
K N
KN
Snapper
Marc L
ML
D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis; D003503:Cyclobutanes / Q000737:chemistry*; D003516:Cycloparaffins / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry; D008958:Models, Molecular; D013816:Thermodynamics
D001643:Bridged Bicyclo Compounds; D003503:Cyclobutanes; D003516:Cycloparaffins; D004987:Ethers