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Oxa-bis-and Oxa-tris-u/n-homobenzenes Syntheses and a + n-IsomerhitionsAddition of diazomethane to the benzene oxides 13a-d yields -under the cis-directing influence of the oxirane oxygen atom often stereoselcciively -the cis-mono- (16% c, d), the cis-bis-(17a-c) and the rr.utis-bis-l-pyrazolines 19b. Photolysis of 16a.c.d. of 17b.c. and of 19b proceeds exclusively to the oxa-bis-a-homohenzenes 20a, c, d and the cislrrans-oxa-tris-a-homobenzenes 24b, c and 30b, respectively. In the case of the diester 17a formation of 24. faces competition by H-migration (20e) upon direct excitation, by transannular C -C-bridging (25a) upon acetone-sensitized excitation. The cis-oxa-bis-a-homobenzenes 20a -e thermally isomerize rapidly -and with the exception of 20c -reversibly to the 4H-oxocines 21a-e, the cis-oxatris-a-homobenzenes 24a-c irreversibly to the 4,7-dihydrooxonines 31a-c. In contrast, the equally strained rrans-isomers 30a, b are thermally much more stable and decompose above 180-200°C in an unspecific way. Kinetic and thermodynamic parameters for these 20 + 2n-and 30 + 3n isomerization reactions as well as the spectroscopic data typical of the oxa-bisand oxa-tris-ain-homobenzene structures are presented, the classification of the transformations 24a -c -, 31a-c as [02s + a2s + a2s]-cycloreversions is discussed.

Ausgehend von ,,cis-Benzoltriimin" (3) werden mit 90 -40% Ausbeute die N,N'-disubstituierten Derivate 8 b -f hergestellt. Nitrosierung zu den unterhalb -30 "C 'H-NMR-spektroskopisch identifizierten N-Nitrosoverbindungen 10b -f und N20-Eliminierung fuhren zu den cis-Diazabis-a-homobenzolen (,,cis-Benzoldiiminen") 11 b -f. Deren [,2, + .2, + a2,]-Cycloreversion zu den 1,4-disubstituierten 1,4-Dihydro-1,4-diazocinen 14b -e (11 f liefert -uber 14f? -nur Polymere) ist je nach Art der N-Substitution derart schnell, da8 unter den milden Herstellungsbedin- ( l l f yieldsonly -via 14f? -polymers). With& = 97 + 2 kJ . mol-' (logA = 11.7; AH* = 92 f 2 kJ . mol-'; AS* = -31 f 6 J . K-' . mol-') the most stable cis-benzene diimine l l b is clearly more labile than cis-benzene dioxide. From 14d the diazocine dianion 16 is obtainable by conventional means. The 1,4-dihydro-1 ,4-diazocine parent molecule 5 obtained by protonation of 16 is stable towards acid and base. From this and from systematic 'H-and 13C NMR studies it is concluded, that 5 and its donor-substituted derivatives 14e,g as well as its dianion 16 have a planar structure with strong 10-electron delocalisation (,,aromatic" diaza[8]annulenes) whilst the acceptor-substituted derivatives 14 b -d prefer the twist-boat-chair conformation and are therefore not diatropic.

cis-Triaza-tris-o-homobenzole" (,,cis-Benzoltriimine")Synthesen und [,2, + ,2, + ,2s]-Cycloreversionen zu 4,7-Dihydro-lH-l,4,7-triazoninen i. Br.Eingegangen am 18. Januar 1980 cis-Triaza-tris-o-homobenzol (,,cis-Benzoltriimin") (2) wird ausgehend von cis-Trioxa-tris-ohomobenzol (,,cis-Benzoltrioxid") (1) uber dreifache Epoxidoffnung mit Natriumazid, Tosylierung (92% chiro-/scyNo-Triazido-tritosylate 9 (92 -95070)/11 (5 -8%)) und LAH-Reduktion (40-50%) synthetisiert. Bei pKaI/pKa2-Werten von 6.43 und 1.90 ist mit der speziellen cis-Anordnung der drei Aziridinringe in 2 keine aufiergewtihnliche Basizitat verknupft. Andererseits werden Metall-Ionen leicht komplexiert. Von den dreifach N-akzeptor-bzw. N-donorsubstituierten Derivaten 18b -in gehen beim Erhitzen 18b-jin der Regelhochselektiv die 3 o + 3 n-Isomerisierung zu den 4,7-Dihydro-lH-1,4,7-triazonin-Derivaten 24bj ein. Die Aktivierungsbarrieren sind von der N-Substitution abhangig und sind bei S02R-durchweg hoher als bei COR-oder Alkyl-Substitution. Vor allem auf Grund der kinetischen Daten wird fur die 3 o + 3 n-Umwandlungen 18 -+ 24 in Analogie zu frtiheren Beispielen ein kooperativer Reaktionsablauf uber ,,trishomobenzoide" Ubergangszustande (38) vorgezogen. Mit AH* = 111 & 3kJ .mol-' (AS* = 4 ? 8 J . K -' . mol-' (CD,CN)) fur Mi, als Modell fur 2, besatigt sich, daR der Aziridinring, dem Cyclopropanring vergleichbar, sehr vie1 leichter als der Oxiranring in diesen [& + 2s + 2J-Cycloreversionen partizipiert. %is-Triaza-tris-o-homobenzenes" ("&Benzene Triimine")Syntheses and [Zs + Ss + ,,ZJ-Cycloreversions to 4,7-Dibydro-lH-l,4,7-triazonines cis-Triaza-tris-o-homobenzene ("cis-benzene triimine") (2) has been synthesized from cis-trioxatris-o-homobenzene ("cis-benzene trioxide") (1) via threefold epoxide-ring opening with sodium azide, tosylation (92% chiro-/scyNo-triazido tritosylates 9 (92 -95Vo)/ll (5 -8%)) and LAHreduction (40 -50%). The pKal/pKa2-values of 6.43 and 1.90 show that no extraordinary basicity is connected with the specific orientation of the three aziridine rings. Metal ions, however, are readily complexed. Upon thermal activation, out of the threefold N-donor-and N-acceptorsubstituted derivatives 18 bin, 18 bj undergo, mostly in a highly specific manner, a 3 o + 3 nisomerisation reaction to the 4,7-dihydro-lH-1,4,7-triazonine derivatives 24bj. The activation barriers depend on the nature of the N-substituents and are higher for SO,R than for COR or alkyl groups. Mainly on the basis of the kinetic data and in analogy with earlier examples, a cooperative reaction mechanism via "trishomobenzenoid" transition states (38) is held to be plausible for the 3o+3n-transformations 18-+24. With a AH*-value of 111 f 3 kJ.mo1-l (AS* = 4 8 J . K-' . mol-' (CD,CN)) for 18i, as a model for 2, it is obvious, that the aziridine ring participates much more readily, than the oxirane ring, in these [& + & + &I-cycloreversion reactions and is comparable in this respect to the cyclopropane ring.

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