Table 2. Some physical data o f the dioxetanes 3 and carbonates 4 . 'H-NMR: 200 MHz. in CDCI,. "C-NMR: 50 MHz, in CDCl, (exception 3b: 100 MHz). For the numbering of 3c and 4c see I .

3a: 64%. yellow oil.-'H-NMR (0°C): 6= 1.49 (s; 3H, CH,), 1.56 (s; 3H. CH,), 1 . 7 1 ( ~ ; 3 H , C H ~ ) , 4 . 7 3 ( d , J = 1 1 . 1 Hz; IH,CHZ),4.86(d,J=11.1 Hz; IH.CH:),6.84(d,J=2.1 Hz; IH,3-H),7.12-7.28(m;2H,4-H,5-H7.52(dd, J=7.6 Hz, 1.3 Hz, I H,6-H), 7.65 (d, J=2 .1 Hz; I H, 2-H).-"C-NMR (0°C): 6= 17.97 (q: CH,). 22.25 (q ; CH?), 23.96 (4; CHI), 70.14 (ti CH>), 88.65 (s; C-OO), 89 23 (s: C-OO), 107.08 (d; C-3), 116.62 (d; C-4), 119.51 (d; C-6), 123.23 (d: C-5). 130.14 (s; C-3a), 135.53 (s; C-7), 145.42 (s: C-7a), 145.61 (d ; C-2). 152.73 (s; C-carbonate) 3b: 26%. colorless oil.-'H-NMR (0°C): 6= 1.51 (s; 3H, CHI), 1.58 (s; 3H, CHI), 1.70 ( S ; 3 H, CH,), 4.68 (d, J= 11.2 Hz; 1 H, CHI), 4.91 (d, J= 11.2 Hz; I H, CHz), 6.44 (d, J=9 .6 Hz; 1 H, 3-H), 7.23-7.47 (m; 3H, aryl-H), 7.72 (d, J=9 .6 Hz; I H, 4-H).--"C-NMR (OOC): 6= 17.98 (9 ; CHI), 22.30 (4; CHI), 23.98 (4; CHI), 70.34 (t; CHI), 88.72 (s; C-00) , 89.30 (s; C-00) . 117.35 (d; C-3). 120.20 (s; C-4a), 124.34 (d), 124.85 (d), 125.92 (d), 137.65 (s; C-8a), 143.16 (d; C-4). 145.60 (s), 152.60 (s; C-carbonate), 159.15 (s; C-2) 3c: 35%, colorless needles, m.p. 129- 131 "C (decomp.) (ether/petroleum ether (30-5O0C)).-'H-NMR (0°C): 6 = 1.54 (s; 3H, CHI), 1.62 (5; 3H, CHI), 1.75 ( ~ ; 3 H , C ' H l ) , 4 . 7 6 ( d , J = I l . l Hz; I H , C H ~ ) , 4 . 9 7 ( d , J = I l . I Hz:IH,CH2), 6.41 (d, 3=9.7 Hz; I H, 6-H), 6.89 (d, J=2.2 Hz; 1 H, 3-H), 7.63 (s; 1 H, 4-H), 7.73 (d, 3=2.2 Hz: IH, 2-H), 7.83 (d, J=9.7 Hz; 1 H, 5-H).-I3C-NMR (0°C): 6 = 18.02 (4: CHI), 22.33 (q; CHI), 23.98 (4; CHI), 70.66 (t; CHI), 72.07 (s). 88.68 (5, C-OO), 89.39 (s: C - 0 0 ) , 106.93 (d; C-3), 115.00 (d; C-41, 116.17 (s), 117.54 (d; C-6), 123.06 (s), 125.96 (s), 143.48 (s), 143.97 (d; C-5), 147.44 (d; C-2), 147.84 (s), 152.02 (s; C-carbonate), 159.59 (s; C-7) 4a: 62%, colorless oil.-'H-NMR: 6=2.24 (s; 3H, CHI), 4.81 (s; 2H, CHZ), 6.81 (d: 5 ~ 2 . 2 Hz; I H, 3-H), 7.23 (m; 2 H, 4-H and 5-H), 7.50 (dd, J=6.8 HZ, 2.0 Hz, I H, 6-H), 7.65 (d, J=2.2 Hz; I H, 2-H).-I3CC-NMR: 6=25.99 (4; CHI), 7165 (ti CH?), 107.04 (dd; C-3). 116.76 (d; C-4), 119.48 (d; C-6), 123.26 (d: C-S), 130.29 (s; C-3a), 135.48 (s; C-7), 145.69 (dd; C-2). 152.73 (s; C- carbonate), 200.69 (s: C-carbonyl) 4b: 25% colorless rhombs, m.p. 134- 135°C (ether/petroleum ether (30- 50°C)).- 'H-NMR: 6=2.27 (s; 3 H , CHs), 4.82 ( s ; 2H, CHZ), 6.45 (d, J=9.6 Hz; I H, 3-H), 7.24-7.47 (m; 3H, Aryl-H), 7.74 (d, J=9.6 Hz; 1 H, 4-H).- "C-NMR: 6=26.07 (q; CH,), 71.92 (t; CH2), 117.43 (d; C-3), 120.31 (s; C- 4a), 124.28 (d), 124.79 (d), 125.86 (d), 137.89 (s; C-8a). 143.02 (d; C-4), 145.78 (s), 152.48 ( s ; C-carbonate), 158.97 (s; C-2). 200.81 (s; C-carbonyl) 4c: 35%, colorless needles, m.p. 145-147°C (ether).-'H-NMR: 6=2.31 (s; 3H, CH,), 4.85 ( S ; 2H, CHI), 6.38 (d, J=9.7 Hz; I H, 6-H), 6.87 (d, J=2.2 Hz; I H, 3-H), 7.60 (s: I H, 4-H), 7.73 (d, J=2.2 Hz; 1 H, 2-H), 7.79 (d, J=9.7 Hz; 1 H, 5-H).-"C-NMR: 6=26.15 (9: CH,), 72.18 (t; CHI), 106.90 (d; C- 3), 115.1 I (d ; C-4), 116.30 (s), 117.52 (d; C-6). 126.07 (s), 143.65 (s), 143.83 (d; C-51, 147.57 (d; C-2), 148.00 (s), 152.02 (s; C-carbonate), 159.37 (s; C-7), 200.93 (s: C-carbonyl)

en-substituted dioxetane 3c is significantly lower. The lower triplet yield (ca. 4%) of 3c should, however, still suf- fice for a photogenotoxic activity.

Received: April 6, 1987; (Z 2181 IE]

German version: Angew. Chem. 99 (1987) 817 revised: May 13, 1987

[I] G. Rodighiero, F. Dall'Aqua, M. A. Pathak in K. C. Smith (Ed.): Topics in Photomedicine. Plenum Press, New York 1984.

121 a) W. Adam, A. Beinhauer, B. Epe, R. Fuchs, A. Griesbeck, H. Hauer, P. Miitzel, L. Nassi, D. Schiffmann, D. Wild in T. Friedberg, F. Oesch (Eds.): Primary Changes and Control Factors in Carcmogenesis. Deutscher Fachschriften-Verlag, Wiesbaden 1986, p. 64-67; b) L. Nassi, D. Schiff- mann, W. Adam, R. Fuchs, A. Favre, Mutation Rex. in press.

131 W. Adam, G. Cilento, Angew. Chem. 95 (1983) 525; Angew. Chem. Int. Ed. Engl. 22 (1983) 529.

[4] a ) W. Adam, V. Bhushan, T. Dirnberger, R. Fuchs, Synthesis 1986. 330; b) W. Adam, V. Bhushan, R. Fuchs, U. Kirchgassner, J. Org. Chem.. in press.

[ 5 ] The compounds were characterized by the 'H- and "C-NMR data given in Table 2 as well as by elemental analyses (C, H i0 .3) and by IR and MS spectral data.

(61 W. Adam, K. Zinner in W. Adam, G. Cilento (Eds.): Chemrcaland Biolog- ical Generation ofExcited States. Academic Press, New York 1982, Chap- ter 5.

[7] A. Beinhauer, unpublished. IS] Chapter 4 in Ref. 161.

Cerium(rv)-Catalyzed Single Electron Transfer (SET) on Acenaphthene and 1,4-Dihydronaphtho- [1,8-d,e][l,2ldiazepine: Chemical Evidence for Distinct Radical Cations** By Waldemar Adam, * Alicia Casado. and Miguel A . Miranda

That the radical cation of acenaphthene (1) is naphtha- lenic-like (structure 1 O@) rather than benzylic-like (struc-

a 1

0 0

ture 20°) has been convincingly demonstrated by ESR and electronic spectra."] However, the question still is open, whether these structures rapidly interconvert and thus exhibit common chemistry, or whether a sufficiently large energy barrier separates them so that they manifest distinct chemical fates. Since a 0-n crossing obtains in the 10@,200 . +- interconversion, the latter behavior is antici- pated. Indeed, we provide herewith experimental proof that the independently generated radical cations 1 Oo and

are discrete species which undergo characteristic 200 reactions.

2 3 4

The azoalkane 2['l was oxidized with ceric ammonium nitrate in oxygen-saturated 80% aqueous methanol at 20°C, a potent single electron transfer (SET) oxidant that proved effective for the denitrogenation of azoalkanes['I and the cleavage of carbon-carbon bonds in 1,2-diaryl- ethanesI4' via the corresponding radical cations. Within 5 min complete nitrogen loss ensued and upon silica gel column chromatography the previously unknown methoxy aldehyde 3IS1 could be isolated in 25% yield and the lac- tone 4I6l in 18% yield. Significant is that only traces of acenaphthene-derived products were observed. Further- more, the triphenylpyrylium tetrafluoroborate(TPT)-sensi- tized photolysis of azoalkane 2, which proved successful for the denitrogenation of cyclic azoalkanes via radical cations,"] led exclusively to the tautomeric hydrazone.

To account for the products 3 and 4, it is postulated that the benzylic-type radical cation 2@' intervenes, which after trapping by methanol and molecular oxygen leads to

[*] Prof. Dr. W. Adam, A. Casado lnstitut fur Organische Chemie der Universitat Am Hubland, D-8700 Wiirzburg (FRG) Prof. Dr. M. A. Miranda Department of Organic Chemistry, Faculty of Pharmacy University of Valencia, E-46010 Valencia (Spain)

[**I This work was supported by the Alexander-von-Humboldt Foundation ( M . A . M. ) , by the Deutschen Akademischen Austauschdienst ( A . C.) , as well as by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

Angew Chem In1 Ed Engl 26 (1987) No. 8 0 VCH Verlagsgesellschaft mbH. 0-6940 Wernherm. 1987 0044-8249/87/0808-0797 $ 02.50/0 797

the methoxy aldehyde 3. Trapping of the radical cation 2" with water and oxygenation affords first the corre- sponding hydroxy aldehyde, which is further oxidized to the lactone 4 via the hemiacetal. Related chemistry was re- ported for the Ce( ~ v ) - c a t a l y z e d ~ ~ ~ and 1,4-dicyanonaphthal- ene-photosensitizediX1 oxidation of 1,2-diarylethanes, ex- cept that the intervening radical cation had suffered rup- ture of the ethane bond since trapping products of the re- sulting benzyl cations and radicals were observed.

Oxidation of acenaphthene (1) with ceric ammonium ni- trate in oxygen-saturated 80% aqueous methanol furnished methyl ether 5 (14%), alcohol 6 (12%), and ketone 7 (59%), all identified by comparison of TLC retention times and spectral data with those of the authentic materials. Clearly, these products are derived from the naphthalenic-type rad-

5 6 7

ical cation 1 o@,ill which deprotonates to the acenaphthyl radical. Subsequent oxygenation with molecular oxygen affords eventually ketone 7. Alternatively, further oxida- tion affords the acenaphthyl cation which is nucleophili- cally trapped by methanol or water to generate 5 and 6, respectively. Significant is that only traces of ring-cleavage products such as the methoxy aldehyde 3 and lactone 4 were observed.

This dichotomy in chemical behavior in the Ce(iv)-cata- lyzed SET-oxidation of acenaphthene (1) and the azoal- kane 2 is indicative of the structurally distinct radical cat- ions l a@ and 2O@, respectively of the naphthalenic and

benzylic type. An appreciable activation barrier (Ea 2 20 kcal/mol) must separate these two species for characteris- tic chemistry to become observable. At first sight this seems surprising since efficient carbon-carbon bond cleav- age of radical cations derived from diaryIethanes,l4] and more recently benzhydryl derivative^,^'] is well docu- mented. However, in these flexible acyclic radical cations the o-bond to be cleaved can align itself with the aromatic moiety to generate resonance-stabilized 71-type benzyl or benzhydryl radicals and cations. In the rigid naphthalenic radical cation 1 '@ the o-bond is fixed in the plane of the aromatic system, so that overlap of the orbitals of the inci- pient benzylic sites with the aromatic system to form the benzylic radical cation 2'' is only feasible after extensive o-bond rupture. We propose that such 0-71 crossing1Io1 is responsible for the slow 1 O @ * 2 '@ valence isomerization on the chemical time scale. Related cases have been exten- sively investigated concerning photochemical transforma- tions under matrix

Received: April 8, 1987; revised: May 13, 1987 [Z 2187 IE]

German version: Angew. Chem. 99 (1987) 818

[ I ] A. C. Buchanan 111, R. Livingston, A. S. Dworkin, G. P. Smith, J. Phys. Chem. 84 (1980) 423; T. Shida, S. Iwata, 3. Am. Chem. SOC. 95 (1973) 3473: L. Andrews, R. S. Friedman, B. J. Kelsall, J. Phys. Chem. 8 9 ( 1985) 4550.

121 M. Gisin, J. Win , Helu. Chim. Acta 59 (1976) 2273. 131 J. Martelli, R. Gree, J. Chem. SOC. Chem. Commun. 1980. 355; H. Abdal-

lah, R. Gree, R. Carrie, Can. J . Chem. 63 (1985) 3031; A. K. M. M. Ho- que, A. C . Kovelesky, W:K. Lee, H. J. Shine, Tetrahedron Lett. 26 (1985) 5655.

141 W. S. Trahanovsky, D. W. Brixius, J . Am Chem. SOC. 95 (1973) 6778; I . P. Beletskaya, D. 1. Makhon'kov, Rum. Chem. Rev. 50 (1981) 534.

151 3, colorless oil.--'H-NMR (CDCII; 200 MHz): 6 = 10.4 (s; 1 H), 8.10- 7.20(m; 6H), 4.73 (s; 2H), 3.37 (s; 3H).-"C-NMR (CDCI,; 50 MHz): b= 192.1 (d), 143.5 (s), 135.0 ( s ) , 134.6 (s), 131.4 (d), 130.9 (s), 128.3 (d), 128.0 (d), 123.9 (d), 121.4 (d), 121.0 (d), 70.9 (t), 55.5 (9).

161 J. Cason, D. M. Lynch, A. Weiss, J. Org. Chem. 38 (1973) 1944. 171 a) W. Adam, M. Dorr, J. Am. Chem. Soc. 109 (1987) 1570; b) S. C.

181 L. W. Reichel, G. W. Griffin, A. J. Muller, P. K. Das, S. N. Ege, Can. J.

191 A. Okamoto, M. S. Snow, D. R. Arnold, Tetrahedron 42 (1986) 6175. [lo] W. G. Dauben, L. Salem, N. J. Turro, Acc. Chem. Res. 8 (1975) 41; E. M.

Evleth, P. M. Horowitz, T. S. Lee, J. Am. Chem. Soc. 95 (1973) 7948. [ I l l T. Shida, E. Haselbach, T. Bally, Acc. Chem. Res. 17(1984) 180.

Blackstock, J. K. Kochi, ibid. 109 (1987) 2484.

Chem. 62 (1984) 424.

Stable Germaethenes** By Harald Meyer, Gerhard Baum, Werner Massa, and Armin Berndt*

The existence of short lived germaethenes has been de- monstrated by trapping reactions.11.21 We have now pre- pared stable germaethenes and characterized them spec- troscopically, in one case also by a crystal structure analy- sis. Reaction of the electrophilic cryptocarbene 1 ( 2)13] with the germanediylenes 3aI4] and 3bl5] in pentane at room temperature afforded the germaethenes 4a and 4b, respectively, as sole products. The lemon-yellow and pale yellow crystals of 4a and 4b very slowly decolorize on ex-

t B u Me3Si B'

lc<; *,, - / \ L - - J

Me3Si C=B-tBu

1

t B u

t B u I

Me3Si B

Me3Si B

\ / \

/ \ / c c:

I tBu

2

+ :GeR2

3a.b

t B u I 1

Me3Si B R Me3Si B R c o:c-ce/o

R Me3Si 6 R

\ / - \ \ / \ C C = G e \-/ \

+ / \ / \ Me,Si B

I I t B u t B u A 4a.b B

t B u t B u R R I I I /"

C C=Sn c c CI Me,Si \ / \ B / CH(SiMe3)2 Me3Si \ / \ / \ B G e

Me3Si B CH(SiMe3)2 Me3Si B H / \ / \ I \ / \

I I t B u 5

t B u 6a

a , R = N(SiMe,),; b, R, R = NtBu(Si(CH,),)NtBu

['I Prof. Dr. A. Berndt, H. Meyer, G. Baum, Priv.-Doz. Dr. W. Massa Fachbereich Chemie der Universitat Hans-Meerwein-Strasse, D-3550 Marburg (FRG)

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

198 0 VCH Verlagsgesellschafr mbH. 0-6940 Weinheim. 1987 0044-8249/87/0808-0798 $ 02.50/0 Angew. Chem. In,. Ed. Engl. 26 (1987) No. 8