On the mechanism of the Di-. pi. -methane rearrangement of bicyclo(3. 2. 1)octa-2,6-diene: Deuterium labeling and generation of diradical intermediates via photolysis and thermolysis of appropriate azoalkanes

Journal Article · Wed Jul 05 00:00:00 EDT 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00196a030· OSTI ID:7121703

Adam, W; Doerr, M ^[1]; De Lucchi, O ^[2]

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1. Univ. of Wuerzburg (West Germany)
2. Univ. of Sassari, Sardinia (Italy)

The direct (254 nm) and acetone-sensitized (300 nm) photolyses of 2,4,4-trideuteriobicyclo(3.2.1)octa-2,6-diene (D-1) gave exclusively 3,5,5-trideuteriotricyclo(4.2.0.0)oct-3-ene (D-7) and 2,6,6-trideuteriotricyclo(3.2.1.0)oct-3-ene (D-8) but no rearranged diene, namely, 2,8,8-trideuteriobicyclo(3.2.1)octa-2,6-diene (D-1{prime}). Pyrolysis (400{degree}C) and direct (334 nm) and benzophenone-sensitized (364 nm) photolyses of the azoalkane 3,5,5-trideuterio-9,10-diazatricyclo(4.4.0.0)deca-3,9-diene (D-9) afforded a mixture of tricyclooctenes D-7 (major product) and D-8 and bicyclooctadiene D-1, but no rearranged diene D-1{prime}. These three modes of denitrogenation of the azoalkane 2,2,7-trideuterio-4,5-diazatricyclo(4.3.1.0)deca-4,8-diene (D-10) led only to the tricyclooctene D-8 (major product) and equal amounts of the bicyclooctadienes D-1 and D-1{prime}. Distinct temperature profiles were observed in the product fingerprints of the direct photolysis (334 nm) of the azoalkanes 9 and 10. For both azoalkanes 9 and 10 the quantum yields of denitrogenation increased with rising temperature. In none of these transformations could bicyclo(3.3.0)octa-2,7-diene (2) be detected. These results imply that the di-{pi}-methane rearrangement of the bicyclooctadienes 1 (D-1) and the denitrogenations of the azoalkanes 9 (D-9) and 10 (D-10) are disjoint chemical events. The intervention of diazenyl diradicals (one-bond cleavage of the azoalkanes) is postulated to be responsible for this disparity. The intervention of cyclopropyldicarbinyl diradical 3 as bona fide reaction intermediate in the di-{pi}-methane rearrangement of bicyclooctadiene 1 is questioned.

• OSTI ID: 7121703
• Journal Information: Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 111:14; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400000* -- Chemistry
400200 -- Inorganic
Organic
& Physical Chemistry
400500 -- Photochemistry
640302 -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ALKANES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DATA ANALYSIS
DECOMPOSITION
DEUTERIUM COMPOUNDS
DIENES
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
KINETICS
MEASURING INSTRUMENTS
MEASURING METHODS
METHANE
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
POLYENES
REACTION KINETICS