[ I ] D . Seebach, E. Hungerbiihler in R. Scheflold: Modern Synthetic Methods, Vol. 2, Salle und Sauerlander, Aarau 1980, p. 91.

121 a) A. Nordal. G. Hausfreif, J . Grether. Medd. Nor. Farm. Selsk. 28, 225 (1966); b) S . Sakamura, T. Yoshihara, K . Toyoda, Agric. Biol. Chem. 37, 1915 (1973); 33. 1795 (1969); c) R. W. Gray, A. Guggisberg, K. P. Sege- barth. M. Hesse. H . Schmid, Helv. Chim. Acta 59, 645 (1976).

131 Precursor of (2a): M. Carmack, C. J. KeNey, J. Org. Chem. 33, 2171 (1968); D. Seebach. H . - 0 . Kalinowski. 8. Bastani. G. Crass, H . Daum. H. Dorr. N . P. Du Preez. V. Ehrig, W. Langer, C. Niissler. H.-A. Oei. M. Schmitt, Helv. Chim. Acta 60, 301 (1977); J. A . Musich. H . Rapoport. J. Am. Chem. SOC. 100. 4865 (1978);-Precursor of (2b) by titanate cata- lyzed transesterification of the methyl ester: D. Seebach, E. Hungerbuhler, R. NaeJ P. Schnurrenberger, B. Weidmann, M. Ziiger. Synthesis, in press.

[4] Cf.: A. B. Smith. 111. P. J. Jerris, Synth. Commun. 8, 421 (1978); J. Mulz- er. T. Kerkmann. Angew. Chem. 92. 470 (1980); Angew. Chem. Int. Ed. Engl. 19. 466 (1980); J. E. Baldwin, J. Chem. SOC. Chem. Commun. 1976, 734, 736, 738.

[5 ] W. HeNer. Ch. Tamm, Helv. Chim. Acta 57, 1766 (1974). We thank Prof. Ch. Tamm. Universitat Basel, for an authentic sample of dimethyl (2R,3S)-( +)-4'-Omethylpiscidate.

Dihydrodioxetobenzodioxins : Synthesis and Chemiluminescence"*' By Waldemar Adam, Omar Cueto, Ernst Schmidt, and Kiyoshige Takayama"l

In our search for novel "high-energy'' molecules for the thermal generation of electronically excited products, we undertook the preparation of the dioxetanes (I) derived from 1,4-benzodioxins (4). By analogy to the perhydro- dioxetodioxins (2) and the bisdioxetane (3). which on ther- molysis afford electronically excited ethylene glycol dies- ter''] and benzoic anhydrideI2], respectively, in high yield, it was expected that electronically excited pyrocatechol dies- ters should be formed in high yields from 2a,8a-dihydro- I ,2-dioxeto[3,4-a][ I ,4]benzodioxin (])I3]. Herewith we re- port the preparation, characterization, and chemilumines- cence of the novel dioxetanes ( I ) .

R P h - P h

Photosensitized singlet oxygenation of a 0.03 M CHzClz solution of the 1,Cbenzodioxins (4)141 at - 78 " C , using po- lymer-bound Rose Bengal as sensitizer and a 400W so- dium street lamp as radiation source['I, led to complete consumption of the dioxins within 2 h, as evidenced by NMR monitoring. For example, with (4a) the olefinic pro- ton at 6= 6.41 disappeared with simultaneous appearance of the dioxetanyl proton at 6=6.33. On heating to 20°C this signal also disappeared; in its place an aldehydic pro- ton-as expected for (5a)-appeared.

The dioxetane (la). was isolated by column chromatog- raphy (Florisil, - 60 "C, CH,CI,) and characterized spec-

[*] Prof. Dr. W. Adam, Dr. 0. Cuerto, DipLChem. E. Schmidt, Dr. K. Takayama lnstitut fur Organische Chemie der Universitat Am Hubland, D-8700 Wiirzburg (Germany) (address to which corre- spondence should be sent) Department of Chemistry, University of Puerto Rico Rio Piedras, Pueno Rico (USA)

[**I This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, the National Science Foundation, the National Institutes of Health, as well as by the Petroleum Research Fund.

troscopically'". On heating, pure (la) quantitatively gave the pyrocatechol diester ( 5 ~ ) ' ~ ~ with concomitant light emission.

4) f J ) (51

( a ) , R = Ph, R'= H; (b ) , R = Ph, R ' = Me; I c ) . R = R ' = Me

Photooxygenation of 2-methyl-3-phenyl and 2,3-dime- thyl- 1,4-benzodioxins, (46) and (4c). respectively, afforded the corresponding dioxetanes (Ib)'*l and (lc)I9l which upon heating were quantitatively transformed into the pyrocate- chol derivatives (5b)'''' and (5~)" 'I, respectively, with light emission.

On thermal decomposition, the dioxetanes (I) chemilu- minesce; however, the emission intensity was too weak to be useful for quantitative determination of the singlet quantum yields (a'). We therefore used the energy-trans- fer chemiluminescence to assess the quantum yields'". The activation parameters AHf and AS', and the singlet (<pLpA) and triplet (aTSA) quantum yields, respectively, are collected in Table 1 .

Table I . Activation parameters and quantum yields for thermolysis of the dioxetanes ( I ) .

(10) (Ib) ( I d ~ ~~

25.1 f 1 26.2 f I 23.8 f I .O AHC [kcal/mol] [a]

AG+[kcal/mol] [b] 25.1 f 1 26.9 f 1 27.3 f 1 AS' [cal/mol/K] [a] -5 . I f2 -5.7It2 -3.7 *2

103 a:,Ph [%I 1.1 f 0 . 3 1.6f0.2 0.09 * 0.02 @;>BA [%I 0.6f0.06 3.5f 1.3 0.02 f 0.0 1

0.6 f 0.06 3.5f 1.3 0.02 * 0.01 (Dl+\ 0

uJT/aJ' 500 f 3 0 0 2200 f700 200 * I 0 0 1 4

[a] Determined by isothermal kinetics using DBA-enhanced chemilumines- cence. @] At 293.2 K.

The activation parameters show that the dioxetanes (1) are of comparable stability to that of tetramethyl-l,2-diox- etane (TMD)131. As expected, the disubstituted dioxetanes (lb) and (lc) are more stable than the monosubstituted de- rivative (la). but there is no difference in stability due to phenyl uersus methyl substitution. From the quantum yields it is seen that, as with TMD, n,x* triplet states can be selectively generated from the dioxetanes (I), i. e. all de- rivatives (la)-(lc) give very low yields of n,x* singlet states. Surprising is the very low total quantum yield of dioxetane (Ic). The possibility of introducing substituents into the benzene ring and at the 2,3-positions should make derivatives assessible which exhibit high singlet excitation yields through intramolecular electron exchangef'].

Received: February 12, 1980, [Z 924 IE]

German version: Angew. Chem. 93. I100 (1981) in altered form July 5, 1981

CAS-Registry numbers: (la), 79792-88-4; (Ib). 79792-89-5; (lc). 79792-90-8; (40). 5770-58- I ; (46). 79792-91 -9; ( 4 ~ ) . 79792-92-0; (5a). 79792-93-1 ; (Sb), 79792-94-2; (Sc). 635.67- 6.

[I] K . A. Zaklika. A. L. Thayer, A. P. Schaap. J. Am. Chem. SOC. 100. 4916 (1978).

121 W. Adam, C . 4 . Cheng, 0. Cueto, I . Erden. K. Zinner. J. Am. Chem. SOC. 101. 4735 (1979).

131 W. Adam, Adv. Heterocycl. Chem. 21. 437 (1977).

Angew. Chem. fnr Ed. Engl. 20 (1981) No. 12 0 Verlag Chemie GmbH. 6940 Weinheim, 1981 0570-0833/81/1212-1031 $02.50/0 1031

141 For the synthesis of 1,4-benzodioxins cf. E. Schrnidf. Diplomarbeit, Uni- versity of Wiirrburg 1981.

151 W. Adam, H. J . Eggelte, J. Org. Chem. 42, 3987 (1977). [6] ( I f f ) . 41% yield, yellow crystalline solid, m.p.=70-72"C (n-

CSHIL/CHICL), >98% peroxide content by iodometric titration, satis- factory elemental analysis; 'H-NMR (CCI,, TMS): 6=6.33 (I H, s, 4 - H ) , 7.16 (4H, s, arom. protons), 7.45-7.61 and 7.83-7.97 (5H, m, phenyl); IR (CCI,): v=3080,2960, 1620, 1500, 1470, 1460 cm-' .

171 (Sa). 82% yield, b.p.= 110°C/0.15 torr, n$= 1.5701; satisfactory ele- mental analysis; 'H-NMR (CCI,, TMS): 6=7.00--7.50 and 7.90-8.09 (SH, m, phenyl), 7.12 (4H, s, arom. protons), 7.95 ( I H, s, H-C02); IR (CCI,): v=3080 (aromatic CH), 1750 ( C 4 ) cm-'.

IS] (Ib). 35% yield, yellow crystalline solid, m.p.=72-76"C (n- C S H I ~ K H ~ C I ~ ) , >98% peroxide content by iodometric titration, satis- factory elemental analysis: 'H-NMR (CCI4, TMS): 6= 1.41 (3H, s, CH,), 7.06 (4H, s, arom. protons), 7.40-7.57 and 7.73-7.88 ( 5 H, m, phenyl); IR (CCI,): 3080, 2950, 1615, 1495, 1455, 1395 cm-' .

191 (lc), 33% yield, yellow crystalline solid, m. p. = 1 18 - 122 "C (dec.) (n- C5HI2/CH2CI2), satisfactory elemental analysis; 'H-NMR (CCI,, TMS): 6= 1.81 (6H, s, CHJ and 6.99 (4H, s, arom. protons); IR (CCI,): 3040, 3000, 1612, 1495, and 1264 cm-'.

[lo] (Sb), 83% yield, b.p. = 15OoC/0.IO torr, RE'= 1.5631, satisfactory elemen- tal analysis; 'H-NMR (CCI,, TMS): 6=2.15 (3H, s, CH,), 7.45 (4H, s, arom. protons), 7.65-7.87 and 8.30-8.35 (SH, m, phenyl); IR (CCI,): 3080, 2960, 1775, 1755 cm-'.

[ I I ] (5c) formed quantitatively and IR and 'H-NMR identical with literature data, H. Nimr. K. Das. N. M. Minernura. Chem. Ber. 104, 1871 (1971).

Donor- Acceptor-Stabilized 1,6-MethanoflOlannulene Derivatives'"' By Richard Neidlein and Hartmut Zeiner"' Dedicated to Professor Rolf Huisgen on the occasion of his 60th birthday

The diketo derivative (la) of 1,6-methano[ IO]annulene, a homologue of 1,4-naphthoquinone, cannot be synthe- sized"] since it is thermodynamically less stable than its valence isomer (lb).

In contrast, however, the bicyclic quinoid structure is considerably more stable than the tricyclic structure if it is incorporated into an integral part of a ''push-pull'' system as in (2a). No evidence that the valence isomer (2b) exists has been obtained to datei2]. To the best of our knowledge, (2a) is the first "push-pull"-stabilized quinomethide whose

['I Prof. Dr. R. Neidlein, Dr. H. Zeiner Pharmazeutisch-chemisches lnstitut der Universitat Im Neuenheimer Feld 364, D-6900 Heidelberg (Germany)

by the Deutsche Forschungsgemeinschaft. ["I This work was supported by the Fonds der Chemischen Industrie and

quinoid partial structure is not derived from a benzoid aro- matic system.

The synthetic route to (2a) starting from the tautomerid valence isomeric mixture (-?)I3] is outlined in Scheme I .

x@ (2c)

Scheme 1. A: 5-methyl-1.3-benzodithiolylium perchlorate 141, anhydrous CH,CN, N2, 20"C, 12 h; B: NEt,, CH2C12, 20°C; C: Reaction to give (5) or (6): dicyanoketene [5] or 9-carbonylfluorene [6], anhydrous toluene, N2, 1.5 - 2 h.

The bicyclic cycloheptatriene structure of (2a) is based on spectroscopic evidence: in the 'H-NMR spectrum, the CH,-bridge protons form an AX system with geminal cou- pling 2JAx=10.7 Hz; in contrast, 4-5 Hz would be ex- pected for a tricyclic norcaradiene structure such as in (2b)[71. A further index for (2a) is provided by the absorp- tion of H-7 to H-10[81 (ABCD system at relatively low field strengthL6.7). The "push-pull" effect in (24 produces a carbonyl absorption at conspicuously low wavenumber, as well as a relatively high basicity; the negative solvato- chromism of the longest wavelength UV bands indicates a marked contribution of the polar mesomeric structure (2a') to the ground state.

Conversion of the basic (2a) into the conjugated red-vio- let acid (2c) (Scheme 1) shifts the absorption of the CH2- bridge protons (AB signal) 1.18 ppm upfield. With

Table 1. Selected physical data for compounds (2a). (5). and (6).

(20): M.p.=70-71°C: yield 82%; Mf =322.0485 (calc. 322.0484); 'H- NMR (90 MHz, CDCI3, TMS): 6=0.65 (d, AX signal, %,= 10.7 Hz, I H, CH,), 3.29 (d, AX-signal, 'JAx= 10.7 Hz, 1 H, CH,), 2.37 (s, CH,), 5.85 (d, AB signal, 3J3.4= 11.8 Hz, H-41, 7.29 (d, AB-signal, '.I3,= 11.8 Hz, H-3). 6.86- 7.34 (m, H-7 to H-I0 and 3 arom. H) 181; UV (CH,CN): d,,,=244 nm

254 (10655, sh), 295 (4364, sh), 316 (3540, sh), 458 (9253); IR (KBr): 1610 cm-' (CO), 1535 ( C 4 ) ; MS (100 eV, 170°C): rn/r 322 (IWh, M') (2c)G(2a) in CFKOOD: 'H-NMR (90 MHz, TMS): 6=0.21 (d, AB-signal, 'JAB= 10.8 Hz, 1 H, CH,), 1.37 (d, AB-signal, 2JAB= 10.8 Hz, I H, CH,), 2.63 (s, CH,), 6.63 (6,,, ,J3.4= 10.2 Hz, H-4), 7.34-8.19 (m, H-3, H-7 to H-I0 and 3 arom. H) (5): yield 52%; M+ =370.0597 (calc. 370.0597); 'H-NMR (90 MHz, CD,C12, TMS): 6=0.80 (d, AX signal, ,JAx=10.9 Hz, 1 H, CH,), 2.75 (d, AX signal, 'JAx=10.9Hz, 1H,CHz),2.39(s,CH,),6.49(d,ABsignal,'J,.4=11.1 Hz,H- 4), 6.98 (d, AB signal, 'Ju= 11.1 Hz, H-3), 7.05-7.46 (m, H-7 to H-10 and 3 arom. H) (6): M.p.= 128°C;yield46%; 'H-NMR(90 MHz,CDC13,TMS):6=0.89(d, AX system, 'JAX = 10.6 Hz, I H, CH2), 3.22 (d, AX signal, 2JAx = 10.6 Hz, I H, CH2), 2.32 (s, C H A 6.50 'J3..,= 11.6 Hz, H-4). 6.86-7.86 (m, H-3, H-7 to H-10 and I I arom. H): UV (CH3CN): d,.,=204 nm (&=74976), 230 (72179). 252 (43083). 264 (34131, sh), 318 (3917, sh), 340 (3357, sh), 522 (16226); UV (CH2C12): d2,:,,=305 nm (~=13885, sh), 322 (7295, sh), 342 (5648, sh), 540 (17415); MS (100 eV, 250°C): rn/r 470 (62%, M')

(E= 10094). 316 (3154, sh), 445 (8306); UV (CH2CI2): d.,,,=245 (11 478, sh),

1032 8 Verlag Chernie GmbH. 6940 Weinheirn, 1981 0570-0833/81/1212-1032 $ 02.50/0 Angew. Chem. Inl. Ed. Engl. 20 (t98t) No. 12