title: Substituent effect of group 14 elements on the ring-opening reaction of cyclobutene.
abstract: A series of cyclobutenes bearing group 14 elements at the 3-position were synthesized, and their thermal ring-opening reactions were studied. Carbon-substituted cyclobutene underwent the ring-opening reaction through an outward pathway to afford the E-diene exclusively. On the other hand, the ring-opening reaction of the silyl, germyl, and stannyl substituted cyclobutenes occurred in both outward and inward directions giving a mixture of E and Z isomers. The structural features of the calculated transition state and population analysis suggested that the formation of the Z-isomer could be ascribed to the donor/acceptor interaction between the HOMO and the sigma(*) orbital of group 14 elements. Interestingly, the order of inward preference was Si > Sn > Ge. These rotational behaviors of silyl, germyl, and stannyl substituents were explained by taking into account the energy gap and the magnitude of overlap between the sigma(*) orbital and HOMO.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan.
authors.forename: Munehiro
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Ippei
authors.initials: I
authors.lastname: Usui
authors.forename: Soichiro
authors.initials: S
authors.lastname: Konno
authors.forename: Masahiro
authors.initials: M
authors.lastname: Murakami
mesh_terms: D003198:Computer Simulation; D003503:Cyclobutanes / Q000138:chemical synthesis / Q000737:chemistry*; D005857:Germanium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012825:Silicon / Q000737:chemistry*; D013237:Stereoisomerism; D014001:Tin / Q000737:chemistry*
chemical_list: D003503:Cyclobutanes; D009942:Organometallic Compounds; D005857:Germanium; D014001:Tin; D012825:Silicon