11‐Methylene‐1,6‐methano[10]annulene and 1,6‐Methano[10]annulen‐11‐ol

Abstract

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...

The Oxidation of Organic Compounds by Active Manganese Dioxide

“…283.466.468.495.5 1 1. 512 Vogel and co-workers S12 in their comprehensive study of chemistry of a novel lO1t-electron annulene system (e.g., 1.6-methanocyclodecapentaene) observed an unusual type of aromatic isomerization. for example.…”

Stabilized and Destabilized Carbocations in the 1,6-Methano[10]annulene Series

“…Answers to these questions were sought by examining the chemistry of triflate 42 . The preparation of 42 utilized the acetate 40 , which is available from a silver acetate assisted solvolysis reaction of 11-bromo-1,6-methano[10]annulene in acetic acid . This silver-assisted reaction may well involve the carbocation 6 , or at least a transition state with cationic character at the 11-position.…”