title: Studies on thermal reactivity of beta-(1,2-allenyl)butenolides and 2-allyl-3-allenylcyclohex-2-enones.
abstract: A series of thermal pericyclic reactions of beta-allenylfuranones have been studied. It was observed that beta-allenylfuranones would undergo 1,5-hydrogen shift to afford a new type of trienes upon heating. Due to their high reactivity, these trienes would undergo subsequent pericyclic reactions based on the nature of the substituent group R: When R is an alkyl group, the intermediate 4a or 4b would undergo a further 1,7-hydrogen shift to afford a more stable conjugated triene 3; with R being phenyl or cyclopropyl group, the 1,7-hydrogen shift was inhibited and the 4-type conjugated triene would form a six-membered ring 5 via 6 pi-electrocyclization. Interestingly, introducing another C=C double bond into the triene intermediate (R = CH=CH2, the 18-type intermediate would undergo 8 pi-electrocyclization reaction to form an eight-membered ring. Such a transformation was also observed with 2-allyl-3-allenylcyclohex-2-enones. The deuterium-labeling mechanistic studies show that the alkyl groups at the allenyl moiety of 1 participated in the isomerization process via 1,7-hydrogen shifts between 18 A, 20 A, and 29 A.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, PR China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Gu
authors.forename: Shengming
authors.initials: S
authors.lastname: Ma
mesh_terms: D000466:Alkadienes / Q000737:chemistry*; D000478:Alkylation; D018360:Crystallography, X-Ray; D003510:Cyclohexanes / Q000737:chemistry*; D004583:Electrons; D005663:Furans / Q000737:chemistry; D006589:Hexestrol / Q000031:analogs & derivatives* / Q000737:chemistry; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D013696:Temperature
chemical_list: D000466:Alkadienes; D003510:Cyclohexanes; D005663:Furans; D006589:Hexestrol; C506365:Cyclohexane; C025947:propadiene; C031597:butestrol