AND 7-PH!NTLCTCLOHIPTA-1,3,5-TRIIN!S FRON B!NZVAL!NI VIA 3,3A,,,5,5, &A 4 H!XAHYDRO·•,S,&-M!TH!NOCYCLOPBNTAPYRAZOLIS and TBTRACYCLO[ •
Tetrahedron Vol. 45, No. 10, pp. 2905 to 2915, 1989 0040-4020/89 $3.00+.00 Printed in Great Britain. © 1989 Pergarnon Press plc 7-M!THYL- AND 7-PH!NTLCTCLOHIPTA-1,3,5-TRIIN!S FRON B!NZVAL!NI VIA 3,3a,,,5,5, &a 4 H!XAHYDRO·•,s,&-M!TH!NOCYCLOPBNTAPYRAZOLIS AND TBTRACYCLO[ •. 1. 0.01 ' • 0~' 1 lHIPTAHIS MANFRED CHRIStL••, ERICH BRUNN•, WOLFGANG R. ROTH~, AND HANS-WERHER LENNARTZ' Institut für Organische Chemie der Universität Würzburg•, Am Hubland, D-8700 Würzburg, Federal Republ ic of Germany Fakultät für Chemie der Universität Bochum~, Postfach 102148, D-4630 Bochum 1, Federal Republic of Germany (Received in Belgium 8 August 1988) Abstract: The addition of benzvalene < n to diazomethane, diazoethane, 2- diazopropane, phenyldiazomethane, and diphenyldiazomethane afforded the 1-pyrazolines 2a-; in good yields. By means of competition experiments, the relative reactivities of benzvalene 111 and norbornene with regard to diazomethane and 2-diazopropane have been determined. The fact that benz valene reacts about twice as fast as norbornene with both diazoalkanes cannot be rationalized on the basis of frontier orbital energies. On direct photolysis, the pyrazolines 2a-; were converted into the tetracy 2 4 3 clo[ 4. 1. 0. 0 • • 0 •., l heptanes 4a-; exclusi vely. These compounds gave the 1,3,5-cycloheptatrienes !5a,b,d,t,; in high yields on treatment with sil ver ions, thus providing better access to 7, 7-dimethyl-( Sdl and 7.7- diphenylcycloheptatriene C 5;1 than before. Su1•prisingly. the latter com pound is in equilibrium with a substantial Quantity of the norcaradiene form.
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