No amino or hydroxy derivative of 1,6-methano-[ll or 1,6epoxy- [lO]annulene [21, 1,2,8,9-tetradehydro[l4]annulene[31, or dihydro-trans-15,16-dimethylpyrene 141 has yet been described. [11(1) and thionyl chloride give the acid chloride (b.p. 97-98 "CjO.02 mm Hg; yield 92 %), which in a Curtius reaction with sodium azide in boiling toluene affords the isocyanate (2) as a pale yellow liquid (b.p. 69-72°C/0.01 mm Hg; 9 0 % yield), whose N M R spectrum (in C a 4 ) contains a multiplet at T = 2.2-3.5 and an AB system with its center at T = 10.6 (proton ratio 7:2); the derived methylurethane has m.p. 145-146 "C.
1,6-Methano[lO]annulene-2-carboxylic acid
qOOH N=C=O(1)Treating the isocyanate (2) with dilute NaOH (formation of the sodium carbamate) and then with dilute H2SO4 in amount equivalent to the alkali affords an orange-yellow, air-sensitive, basic substance (yield 85 %), b.p. 97-98 "C/0.07 mm Hg [UV spectrum in cyclohexane: A, , , = 254 (E = 32,000), 270 (21,OOO)(sh), 342 (5500), and 415 m p (llOO)]. The N M R spectrum of this product in CCI4 contains a multiplet at = 2.5-4.2 (7 vinyl protons), a broad singlet at T = 6.2 (2 amino protons), and an AB system at T = 10.0 and 10.85 with JAB = 9.5 Hz (CHz protons) and thus shows the presence of 1,6-methano[lO]annulen-2-amine (3), free from imino tautomers. The amine was characterized as hydrochloride and acetyl derivative (m.p. 204 "C), but attempts to diazotize it had no clear result.When the aqueous solution of the hydrochloride of (3) is heated in the presence of toluene a keto-enol mixture is obtained from which the ketone can be crystallized (m.p. 26 "C). It can be concluded from the N M R spectrum of the ketone (Fig. 1) that the hydrolysis involved not only tautomerization but also cycloheptatriene-norcaradiene valence isomerization, because the AX system at T = 7.9 and T = 9.8 with J A X = 4.5 Hz can be assigned unambiguously to CH2 protons in a cyclopropane ringrsl. When it is further considered that the UV spectrum (in cyclohexane) with Amax = 215 (E = 11,600), 274 (2600), and 320 m p (180) is to be interpreted as superposition of the absorption bands of a norcaradiene systemL61 and an or$-unsaturated carbonyl group (CO band at 1660 cm-I), then the ketone must be tricyclo[4.4.1.01~6]undeca-3,7,9-trien-2-one (4).In the presence of catalytic amounts of acid or base the ketone (4) is equilibrated with the enol, which is proved to be 1,6methano [lO]annulen-2-01 by its NMR spectrum (Fig. 1). The ketone (4) is favored ( = 80 %) in the equilibrium mix-' C = 3 -4 5 / , , i a I I I , , / / 1 J -2 3 4 15 6 i 8 95 70 11 ~~ ~~ Fig. I . N M R spectra [60 MHz; i n (CD,)zSO] of the pure ketone /41 and of the enol-ketone mixture (97:3) obtained by equilibration with catalytic quantities of trimethylamine (OH absorption at 7 -0.1). ture in benzene, but the enol (5) preponderates (97 %) in dimethyl sulfoxide. Catalytic amounts of HCI in methanol cause rapid etherification to 2-methoxy-l,6-methano[lO]annulene.The ketone and the enol are converted by alkali into the intensely yel...
