compounds as 471 components in cycloadditions have, to our knowledge, not been described12! We have now found that the dithionooxalate (2)[3] and the tetrathiooxalate (3)14' undergo numerous cycloadditions Owing to their very reactive dithiabutadiene system. These thioesters may function as 271- or 4~-components, depending upon the reaction partner involved.

68438-1 1-9; (8~),68438-12-0; ( 8 b ) , 68438-13-1 ; (9), 68438-14-2; (lo), 68438- 15-3; ( l l ) , 68438-16-4; ( I Z ) , 68438-17-5; ( 1 3 ) , 68438-18-6; 2,3-dimethylbuta- diene, 51 3-81-5; norbornene, 498-66-8; phenylacetylene, 536-74-3; cyclopen- tene, 142-29-0; cyclopropene, 2781 -85-3; quadricyclane, 278-06-8; I-pentyne, 627-19-0; vinyl ether, 109-92-2; maleic anhydride, 108-31-6

[ l ] a) J . Sauer, Angew. Chem. 78, 233 (1966); Angew. Chem. Int. Ed, Engl. 5, 21 1 (1966); b) J . Homer , J . A . Turner in J . Hamer: 1.4-Cycloaddition Reactions. Academic Press, New York 1967, pp. 205ff.; c) H . Wollweber,

N N H,CO, ,0CH3 Diels-Alder-Reaktion. Thieme, Stuttgart 1972; d) E . Block: Reactions of Organosulfur Compounds. Academic Press, New York 1978, pp. 278ff.

[2] The reaction of bis(diphenylethylenedithio1ato)nickel with norbornadiene reported by G . N. Schrauzer and H . N . Rabinowitz, J. Am. Chem. SOC. 90,4297 (1968), may be regarded as an exception: heating of the com- ponents leads to a cycloadduct of norbornadiene with the, as yet, uniso-

/R R\

F-c* s s R' "2-C' \R * S

( 1 ) ( 2 )

u c c c lated dithiobenzil. L l S L S LJ, u-r 7 $ i q F [3] K . Hartke , H . Hoppe , Chem. Ber. 107, 3121 (1974).

[4] T h . Kissel, R . Mutusch, K . Hartke , Z . Chem. 16, 318 (1976).

In the series (I)-+ (3) , the tetrathiooxalate (3) shows the least resonance stabilization and hence the highest reactivity. Thus, although (3) is monomeric in the crystalline form, in nonpolar solvents such as carbon tetrachloride and tetra- hydrofuran the [4+2] dimer ( 4 ) is already present in equilib- rium at room temperature up to about 20% [ ( 4 ) , 'H-NMR (CCI4): 6=2.10 (C-3-SCH3), 2.42 and 2.49 (C-5-, C-6-SCH3),

Norcaradiene and Cycloheptatrjene Endoperoxides [**I

BY WaLdemar Adam and Metin Bah"' Cycloheptatriene represents a fascinating and challenging

substrate for cycloaddition. Thus its 'norcaradiene valence isomer could give [2+4] adducts of type ( A ) , whereas cyclo-

Table 1 . Experimental data for the formation of cycloaddition products ( 5 ) - ( 1 3 ) . Owing to partial decomposition on distillation the liquid products (yellow oils) could only be purified by chromatography. All the compounds gave correct analyses and IR, 'H-NMR, and "C-NMR spectra consistent with the quoted structures.

r2 XCH, '5 XCH3 E>zt:

( 5 ) 161 1 7 ) ( 8 ) (91

(a ) , Y = 0: Ib). X = s

Product Starting compound Reaction conditions M.p. ["C] Yield ["/.I

( 5 u ) ( 2 ) + 2.3-Dimethylbutad1ene ( 5 b ) ( 3 ) + 2.3-Dimethylbutadiene ( 6 a ) ( 2 ) + Norbornene ( 6 6 ) ( 3 ) + Norbornene ( 7 a ) ( 2 ) + Phenylacetylene ( 7 b ) (3) + Phenylacetylene ( 8 a ) ( 2 ) + Cyclopentene ( 8 b ) (3) + Cyclopentene (9) ( 2 ) + Cyclopropene ( 1 0 ) (2) + Quadricyclane ( 1 1 ) (3) + I-Pentyne ( 1 2 1 ( 3 ) + Ethyl vinyl ether ( 1 3 ) (3) + Maleic anhydride

in ether, reflux, 24 h in CC14, 20°C. 3 h in ether, reflux, 6 h in CC14, 2 0 ° C 1 h without solvent, with A1C13 in CCI4, reflux, 40 h in cyclopentene, reflux, 3 d in cyclopentene, 2 0 T , 72 h in CCI4, O T , gaseous cyclopropene in ether, 20"C, 35 h in l-pentyne/CCI,, reflux, 6 d in ethyl vinyl ether, 30min in CH2C12, 20°C. 2d

oil 56 33 56

138 oil oil oil

52 132 oil oil 102

100 100 77 80 4

ca. 80 67 80 75 87

ca . 50 90 90

2.68 (C(S)SCH,); 13C-NMR (CDZC12): 6= 16.0, 17.8, 20.2, 21.6 (SCH3), 88.4 (C-3), 132.8 and 133.6 (C-5, C-6), 231.2 (C=S)]. Other cycloaddition products with (3) are also formed under milder conditions than with (2). As examples of [4 + 21 cycloadducts of (2) and (3 ) , the compounds (5 ) - (13) have been chosen; the experimental data are listed in Table 1.

Received: September 27, 1978 [Z 104 IE] German version: Angew. Chem. 90, 1016 (1978)

CAS Registry numbers: ( 2 ) , 54129-78-1 ; (3), 61485-47-0; ( 4 ) , 68438-05-1 ; ( 5 a ) . 68438-06-2; ( 5 b ) , 68438-07-3; ( 6 u ) , 68438-08-4; ( 6 b ) . 68438-09-5; ( 7 a ) , 68438-10-8; ( 7 b ) ,

heptatriene could yield the uncommon [2+ 61 adducts ( B ) , besides the more normal [2+4]-adducts (C). We now report the successful preparation, isolation, and characterization of

[*I Prof. Dr. W. Adam (NIH Career Awardee, 1975-80), Dr. M. Balci Department of Chemistry, University of Puerto Rico Rio Piedras. Puerto Rico 00931 (USA)

[**I Cyclic Peroxides, Part 77. Acknowledgments are made to the Donors of the Petroleum Research Fund ( 1 1022-AC-I) administered by the American Chemical Society, the National Science Foundation (CHE-78-12621), and the National Institutesof Health(GM-21 119-03, GM-00141-04, and RR-8102- 06).-Part 76: W A d a m and K . Sakanishi, Photochem. Photobiol., in press.

954 Angew. Chem. Int. Ed. Engl. 17 (1978) No. 12

Photooxygenation of cycloheptatriene in CCI, (1 50-W Na lamp) at 0°C and tetraphenylporphyrin as sensitizer, followed by low temperature silica gel chromatography at -50 to -60°C (elution with CH2C12/pentane (1 : 1)) afforded ( 1 ), ( 2 ) , and (3) in 3.5, 37, and 40% yield, respectively. The structure assignments of these unstable endoperoxides rests on 'H-NMR and IR spectral data (Table 1). In addition, the following chemical transformations confirm the proposed structures.

The norcaradiene adduct ( 1 ) led to the saturated. bicyclic peroxide (1 a ) on diazene reduction in methanol at O°C121. Furthermore, on heating in CC1, at 100°C in a sealed tube, ( 1 ) was converted into the hitherto unknown[31 isomer ( I h ) of norcaradiene diepoxide.

Treatment of the unusually strained [2+ 61 cycloadduct (2) with methanol a t 30°C afforded the rearrangement product

the endoperoxides (1 ), (2), and (3)-corresponding to types ( A ) , ( B ) , and (C)-produced by oxygenation of cyclohepta- triene with singlet oxygen. To the best of our knowledge, this constitutes the first observation of all three possible Diels- Alder adducts in a cycloheptatriene cyc1oadditon.-Com- pound (3) has been isolated on photooxidation of cyclohepta- triene in the presence of x-dicarbonyl compounds['"]; (2) and (3) have been postulated as intermediates in the photooxy- genation of cycloheptatriene with singlet oxygen['b1.

Table I . Selected physical data of compounds of types ( I ) to ( 3 ) . The 'H-NMR and IR spectra were recorded in CCll (except for (2b). recorded in CDCI, and CHCI,, respectively).

( I ) : Unstable,m.p.64"C,yield 3.5%; 'H-NMR:6=0.0-0.3(m, lHL0.4- 0.8 (m, I H), 1.4-1.8 (m, 2H), 4.6-4.9 (m, 2H), 6.0-6.3 (dd, 2 H ) ; JAB=

1370cm- I

( l a ) : M.p. 98"C, yield 8 5 % ; 'H-NMR: 6=0.45-1.0 (m, 2H), 1.05-2.2 (m, 6H). 4.0--4.4 (br. s, 2H); IR: 3030, 2945, 2860, 1465, 1350, 1300cm-' ( l h ) : n6'=1.5062, yield 100%; 'H-NMR: 6=0.25--0.55 (m, 1 H), 0.7--1.0 (m,1H),l.1-1.5(m,2H),2.95(s,4H);lR:2980, 1455, 1435, 1420, 1235cm-I; MS (70eV): m/e= 124 ( 2 ) - Unstable, niu=1.5316, yield 37 %; 'H-NMR: 6=2.7--2.9 (4. 2H), 4.3- 4.6 (m. 2H). 5.7-5.8 (m, 4 H ) ; IR: 3030, 2950, 1630, 1440, 1385, 1295~11-l ( 2 ~ ) ' Semisolid, yield 72%; 'H-NMR: 5=0.9-2.0 (m, 8H), 2.1- -~2.8 (m, 2H), 4.2 -4.6 (br. d, J"r=7.01Hz3 2H); JAB=11.66Hz, J A r s 1 . 3 H z ; IR: 2940, 1450. 1265, 1260cm-' ( 2 h ) [la]: Liquid, yield 9 0 % ; 'H-NMR: S=2.4-3.5 (AB, 2H), 3.95 (s, 1 H). 4.3-4.7 (m, I H), 5.4 --6.6 (m. 4H); IR: 3590, 3360. 3010, 1710, 1650, 1575cm I

( 3 ) . Unstable, I @ = 1.5249, yield 40%; 'H-NMR: ri=2.0-3.1 (AB, 2H). 4.2-4.7 (m, 2H), 5.2~-6.7 (m, 4 H ) ; JAB=18.6Hz, JAc:JBr=3Hz, JAG= 2.3 Hz, J,,;=3.99 Hz, J,,= 10.6 Hz, J,,=9.3 Hz; I R : 3070, 3040, 2940, 2890, 1650, 1415cm-I ( 3 ~ ) . M.p. 32- 33"C.yield 3 0 % ; 'H-NMR: &=1.2-2.4 (m, 4H) , 2.2-3.1 (AB, J ~ ~ = 1 6 . 6 H z . 2H). 4.1-4.5 (m. 2H), 5.5-5.9 (m, 2H) ; iR: 3045, 2970, 1650, 1460, 1420, 1 345 cm ( 3 h ) . 116"- 1.5269. yleld 8 2 % ; 'H-NMR: 6=2.2-3.5 (m, 6H). 5.5--6.5 (m. 2H) ; IR: 3030, 3010, 2960, 1690, 1580, 1440cm-l

5.9Hz. J ~ = 6 . 5 H z , J A C = ~ H Z ; IR: 3070, 3040, 3000, 2900, 1530. 1440,

-- ~ ~ ~~~~ -~ ~- ~ ~~~

( 2 b ) . For this reason the diazene reduction had to be carried out in the nonprotic solvent CH2C12 at ca. O"C[41, resulting in the novel bicyclic peroxide ( 2 a ) .

Finally, diazene reduction at 0°C in methanol121 of the [2 +4] cycloadduct (3) led to the expected bicyclic peroxide (3a). On heating in toluene at 180°C in a sealed tube (3) was converted into the epoxyenone (3 b) .

The spectral and chemical data substantiate the novel endo- peroxide structures beyond any reasonable doubt. Thus, ( 1 ) represents the first unsubstituted norcaradiene [2 + 41 cycload- duct, while (2) constitutes the first confirmed [2+ 61 cycload- duct with singlet oxygen. More significantly, photooxygena- tion of cycloheptatriene opens up a convenient entry to unusual bicyclic peroxides which are difficult to prepare by alternative routes.

Received: October 2, 1978 [Z 108 IE] German version: Angew. Chem. YO. 1014 (1978)

[ I ] a) A. Mori. H . Tukeshitu, Chem. Lett. lY78, 395; b) 4. S. K ~ i r d e , J . Y-C. Chu, Tetrahedron Lett. 1970. 4837.

[2] W. Adom, H. J . Egyrlrr, Angew. Chem. 89, 762 (1977); Angew. Chem. Int. Ed. Engl. 16, 713 (1977).

131 E. Vogrl, H. J . Alrenhuch. E. Schniidbauer, Angew. Chem. 85, 862 (1973); Angew. Chem. Int. Ed. Engl. 12, 838 (1973).

[4] M! Adam, H. J . Eggrltr, J . Org. Chem. 42. 3987 (1977).

A i i y w . Chrm. Int. E d . Engl. 17 (1978) No. 12 955