2,3-Dioxa-7-thiabicyclo[2.2.l]heptane: A New Hetero- bicyclic System Possessing the Thiaozonide Struc- ture[**] By Waldemar Adam and Henny J . Eggelte[*]

To the best of our knowledge thiaozonides possessing the 2,3-dioxa-7-thiabicyclo[2.2.l]heptane structure (3) are unknown. The only related substance of this type to have been described" is the rather labile and therefore difficult to characterize diphenylacenaphthylene derivative (8).

We now wish to report that thiaozonides ( 3 a ) and ( 3 b ) can be prepared in good yields, isolated, and characterized. We have also found that oxidation of electron-rich thiophenes (I ) with singlet oxygen affords the postulated highly reactive thiophene endoperoxides ( 2 ) , and that peracid oxidation of the thiaozonides (3) leads to 1,4-diones (6) by sulfur dioxide elimination, presumably uia the unusual sulfones (7).

R Q - 78°C

R

R

s~ P h

R C O J H - 40 "C 1

0 &I R

(7)

(a ) , R = CH3; ( b ) , R = C(CH3),

Alkyl-substituted thiophenes ( I ) undergo photosensitized reaction with singlet oxygen to afford 2-butene-I ,4-dione derivatives ( 4 ) and sulfenes (5)[21, which presumably arise from the labile, intermediary thiophene endoperoxides (2) by thermal loss of sulfur or rearrangement, respectively. If the endoperoxides (2) really are reaction intermediates in the photooxygenation of thiophenes (I), then it should be possible to reductively trap them with diazene, as recently demonstrated for the unstable endoperoxides of cyclopenta- dieneL3"], ~pirocycloheptadiene'~~~, f~lvene[~ ' ] , and a-pyr-

Indeed, photooxygenation of 2$dimethylthiophene (I a ) in CH2CI2 at - 78 "C with tetraphenylporphyrin as sensitizer, followed by diazene reduction of ( 2 ~ ) ~ ~ ~ in CH2CI2 at - 78 oC[3a1, gave a 46% overall yield of thiaozonide (3 a ) after silica gel chromatography at -20°C and elution with

['I Prof. Dr. W. Adam (NIH Career Development Awardee, 1975- 1980), Dr. H. J. Eggelte Department of Chemistry University of Puerto Rico Rio Piedras, Puerto Rico 00931 (USA)

[**I Cyclic Peroxides, Part 69. Acknowledgements are made to the Donors of the Petroleum Research Fund (Grant 8341-AC-1,4), administered by the American Chemical Society, the National Science Foundation (Grant CHE- 77-1 3308). and the National Institutes of Health (Grants GM-21119-03, GM- 00141-02 and RR-8102-03). Part 68: W Adam, K . Sakanishi, I. Am. Chem. SOC. 100. 3965 (1978).

CH2C12[51. This compound is thermally unstable and rapidly decomposes at room temperature to 2,5-hexanedione (6a ) . The same diketone was obtained in essentially quantitative yield by triphenylphosphane desulfurization of (3 a) [61, con- firming the thiaozonide structure (3).

In an analogous manner, 2,5-di-tert-butylthiophene (I b ) was converted into the thiaozonide (3 b ) by diazene reduction of the unstable (2b)[41. Compound ( 3 b ) was isolated by silica gel column chromatography at -20°C with CH2C12 as eluant and could be purified by low temperature recrystalli- zation from pentane. ( 3 b ) is more stable than ( 3 a ) , but also decomposes rapidly to 2,2,7,7-tetramethyl-3,6-octane- dione ( 6 b ) at room temperature. The diketone ( 6 b ) was also obtained in essentially quantitative yield by catalytic hydrogenation over Pd/C, thus confirming the thiaozonide structure (3).

Received: July 10, 1978 [Z 52 IE] German version: Angew. Chem. YO, 811 (1978)

[ I ] J . M. Hoflman, Jr . , R . H . Schlessinger, Tetrahedron Lett. 1970, 797. [2] a ) W J . M. van Tilborg, Rec. Trav. Chim. Pays-Bas 95, 140 (1976).

b) C . N . Skold, R . H . Schlessinger, Tetrahedron Lett. 1970, 791. c) H . H . Wasserman, W Strehlow, ibid. 1970, 795.

[3] a) W. Adam, H . J . Eggelte, J. Org. Chem. 42, 3987 (1977). b) W Adam, 1. E d e n , ibid. 43, 2737 (1978). c) W Adam, I . Erden, Angew. Chem. YO, 210 (1978); Angew. Chem. Int. Ed. Engl. 17, 223 (1978); d) ibid. YO, 21 1 (1978) and 17, 223 (1 978), resp.

decomposes at ca. 0°C. [S] ( 3 ~ ) : yield 46 %, viscous oil, which partially decomposed on short

path distillation at reduced pressure; 'H-NMR (CCI,, TMS) n= 1.75 (s, CH3, 6H), 2.12 (s, CH2, 4H); IR (CC14) 2980, 2940, 2885, 2855. 1445, 1375, 1300. 1200, 1145, 1120, 1060, 890, 845, 600 c m - ' ; ( 3 6 ) : yield 50%. white needles, m.p. 68-69°C (from pentane at -78°C); 'H-NMR (CC14, TMS) 6=1.16 (s, CHJ, 18H), 2.21 (s, CHZ, 4H) ; IR (CCI,) 2970, 2905, 2870, 1460, 1395, 1365, 1185, 1105, 1080, 1040, 900, 630 cm- ' .

~~ ~

[4] ( 2 ~ ) : 'H-NMR (CFCI,,TMS, -21 "C): 6=1.80(s,CH,), 5.78 (s,=CH);

[6] J . Carlea, S. Fliszar, Can. J. Chem. 47, 1 I I3 ( 1 969).

Synthesis and Stereochemical Consequences of Proton- ation of a Bishomodihydrotetraaza[l4]annulene: A New Macrocyclic Complex Ligand[**]

By Helmut Quast, Josef Stawitz, Karl Peters, and Hans Georg uon Schnering['l

Unsaturated fourteen-membered heterocycles having two['] o r four[21 nitrogen atoms are sometimes formed with surprising ease instead of azepines or diazepines despite the absence of transition metal ions acting as template. Derivatives of tetraaza[14]annulenes are of interest because of their ability to complex transition metal ions[31. On preparation of the diazahomotropilidene (2) from cis-I ,2-cyclopropanediamine (I )[41 we observed the formation of bishomodihydrotetra- aza[l4]annulene (5). This compound exhibits a drastic change. of structure on protonation hitherto known only for corres- ponding acyclic compounds such as the base underlying the perchlorate (3 jC5]. Moreover, (5) also warrants attention as

[*] Prof. Dr. H. Quast ['I, Dr. J . Stawitz Institut fur Organische Chemie der Universitat Am Hubland, D-8700 Wiirzhurg (Germany) Dr. K. Peters, Prof. Dr. H. G. von Schnering ['I Max-Planck-Institut fur Festkorperforschung Heisenbergstrasse I , D-7000 Stuttgart 80 (Germany)

[**I This work was supported by the Fonds der Chemischen Industrie. ~~

Someof the results were taken from the Dissertation by J . Stawifz , Universitat Wiirzburg 1978. ['I To whom correspondence should be addressed.

Angeh. Chew? Int. E d . Eiryl. 1 7 (1978) No. 10 765