ISSN:
0009-2940
Keywords:
Cycloheptatriene
;
Norcaradiene
;
Valence isomerization
;
[4 + 2] Cycloadditions
;
Site selectivity
;
Valence isomer selectivity
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
7-Substituted Cycloheptatrienes as Dienophiles in the Diels-Alder Cycloaddition With Inverse Electron DemandA series of 7-substituted cycloheptatrienes 1, including CN, CO2CH3, C6H5, C(CH3)3, CH3, CH(OCH3)2, H, N(CH3)2 groups has been submitted to inverse [4 + 2] cycloaddition with 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine (5). Reaction of 5 with π-acceptor-substituted cycloheptatrienes such as 1a-c leads exclusively to cyclopropa[f]phthalazines 8 and 9, whereas 7-alkylcycloheptatrienes 1d-f give mixtures of cyclopropa[f]phthalazines 10 and 12 and 7H-cyclohepta[d]pyridazines 11 and 13. Moreover, 7-methylcycloheptatriene (1e) yields three further products 19, 20, 21, derived from heptafulvene 16, formed intermediately by dehydrogenation of 1e. In contrast to 1a - f, reaction of 5 with cycloheptatriene (1g) yields the corresponding 5H-cyclohepta[d]pyridazine 22 quantitatively. Surprisingly, no [4 + 2] cycloadducts are observed with the π-donor-substituted cycloheptatriene 1h. Instead, the indazol 27 and the triazoles 25 and 28 are formed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19921250128
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