Pyrolysis of 9-methylenespiro(3. 5)nona-5,7-diene: A route to benzo-2-hexene-1,6-diyl, a putative intermediate in the retro-Diels-Alder reaction of tetralin

Journal Article · Fri Jul 20 00:00:00 EDT 1990 · Journal of Organic Chemistry; (United States)

DOI:https://doi.org/10.1021/jo00302a021· OSTI ID:5955464

Gajewski, J J; Paul, G C ^[1]

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1. Indiana Univ., Bloomington (United States)

A precursor to the 1,6-biradical potentially formed in the retro-Diels-Alder reaction of tetralin, namely, 5-methylenespiro(bicyclo(2.2.1)hept-2-ene-6,1{prime}-cyclobutan)-7-one (9) has been prepared and found to give tetralin and o-allyltoluene upon pyrolysis in solution below 100C and upon flash vacuum pyrolysis around 250C. The product ratio changes from 1:1 to 6:1 at higher temperatures. Rate-determining loss of CO from 9 to give 9-methylenespiro(3.5)nona-5,7-diene, 2, has been demonstrated by trapping the triene with N-methyl- and N-phenyltriazolinedione in a reaction whose rate is independent of trapping agent concentration. The kinetics for loss of ketone, 9, gave log k (s{sup {minus}1}) = 14.628 {plus minus} 0.038-(30.554 {plus minus} 0.064)/2.3RT. Pyrolysis of cis-cyn(to methylene)- and trans-1,2-dimethyl-9-methylenespiro(3.5)nona-5,7-diene gives the vinylcyclobutane rearrangement product, 2,3-dimethyltetralin, with a 4:1 and 2.7:1, respectively, preference for retention over inversion at the migrating carbon. Hydrogen shift products are also formed and by highly ordered transition states. One of these hydrogen shifts involves an unprecedented shift from the carbon remote from the vinyl group.

• OSTI ID: 5955464
• Journal Information: Journal of Organic Chemistry; (United States), Vol. 55:15; ISSN 0022-3263
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYCLOALKENES
PYROLYSIS
TETRALIN
CHEMICAL PREPARATION
ACTIVATION ENERGY
CARBON MONOXIDE
CARBON TETRACHLORIDE
CHEMICAL REACTION KINETICS
DIELS-ALDER REACTION
DIENES
GAS CHROMATOGRAPHY
HYDROGEN TRANSFER
LOW PRESSURE
NMR SPECTRA
REACTION INTERMEDIATES
ALKENES
AROMATICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CHROMATOGRAPHY
DECOMPOSITION
ENERGY
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROAROMATICS
HYDROCARBONS
KINETICS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POLYENES
REACTION KINETICS
SEPARATION PROCESSES
SPECTRA
SYNTHESIS
THERMOCHEMICAL PROCESSES
400201* - Chemical & Physicochemical Properties