[2] For a definition, see M . T Reerz, Tetrahedron 29, 2189 (1973). 131 Related halogen-halogen as well as hylogen- or acetoxy-phenyl exchange

reactions in silicon compounds are known, but have not been studied with regard to their mechanism: W I. Beoun, R. N. Haszeldine, J. Middle- ton, A. E. Tipping, J. Organomet. Chem. 23, C 17 (1970); A. G. Brook, P. f. Jones, J. Chem. SOC. Chem. Commun. 1969, 1323.

141 N. Greg Dissertation, Universitlt Marburg 1977. [ 5 ] The selective thermal transformation of ( 4 b ) into ( 5 b ) has recently

be utilized preparatively: D . J. Ager, I. Fleming, J. Chem. Res. (S) 1977, 6.

[6] Inverted ylides with hypervalent sulfur have recently been isolated: A. J. Arduengo, E. M. Burgess, J. Am. Chem. SOC. 99, 2376 (1977).

171 E. A. I.: Ebsworth in A . G. MacDiarmid. The Bond to Carbon. Dekker, New York 1968, p. 14.

2,3-Dioxabicyclo[2.2.2]octane by Selective Reduction of Double Bonds with Azodicarboxylate[**]

By Waldemar Adam and Henny J . Eggelteyl The peroxide linkage is one of the most susceptible towards

reductive cleavage by a variety of reductants. It is, therefore, not surprising that in the catalytic hydrogenation of unsatu- rated peroxides the peroxide bond as well as the double bond are reduced. If the problem of concurrent peroxide bond reduction could be circumvented in a general and efficient way, this would implement a novel entry into hitherto unknown saturated cyclic peroxides by reduction of the corre- sponding unsaturated precursors, which are readily available by singlet oxygenation"] of suitable cyclic 1,3-diene substrates. Azodicarboxylate is a mild and double bond-specific reduc- tantc2], ideally suited to solve the above synthetic problem. The strategy and execution is outlined below for the two-step conversion of 1,3-cyclohexadiene (1 ) into the previously unknown 2,3-dioxabicyclo[2.2.2]octane (3).

0 2 . hu KOzCN=NC02K

HOAc, 0 "C Rose Bengal

On treatment of the unsaturated cyclic peroxide (2), pre- pared by photo-oxygenation of ( I )r31, with excess azodicar- boxylate in methanol at O0Cl4], the saturated cyclic peroxide (3) was obtained in 48 % yield (m.p. 117-11~"C from hex- ane)[51. On reaction with ethanolic potassium hydroxide the peroxide ( 3 ) is isomerized to the known 4-hydroxycyclohex- anone in high yield, and on catalytic hydrogenation over Pd-C gives quantitatively the known cis-l,4-cyclohexanediol. It is important to mention that submission of pure (3) to the azodicarboxylate reduction conditions did not lead to reduction of the peroxide linkage to give the diol.

The generality of the azodicarboxylate reduction could be demonstrated by preparing dihydroascaridole ( 4 ) , epi- dioxyergosterol acetate (5 ) , and 1,2,3,4-tetrahydro-l,4- dimethyl-l,4-epidioxynaphthalene (6). Thus, the known dihydroascaridole ( 4 ) was obtained quantitatively from ascar- idole, and identified by its characteristic NMR and IR data.

[*] Prof. Dr. W. Adam (NIH Career Development Awardee, l975-1980), Dr. H. J . Eggelte Department of Chemistry University of Puerto Rico Rio Piedras, Puerto Rico 00931 (USA)

[**] Cyclic Peroxides, Part 58. Acknowledgments 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- 72-04956-AO3) and the National Institutes of Health (Grants GM-22119-02, GM-00141-02, and RR-8102-03).-Part 57: W Adam et al., to be published.

Ascaridoleis one of the few cyclic peroxides for which catalytic hydrogenation does not sever the peroxide linkagec6J. The previously unknown ergosterol derivative (5)["] with satu- rated Ring B has now been synthesized for the first time. Even the unstable 1 ,4-dihydro-I ,4-dimethyl-l,4-epidioxynaph- thalene, prepared by photo-oxygenation of 1,4-dimethylnaph- thalene"], could be reduced essentially quantitatively to the novel cyclic peroxide (6)[7bl. It is interesting to note that despite the excess azodicarboxylate that was used, the side chain double bond of ( 5 ) was not reduced. Strained double bonds show a greater reactivity towards azodicarboxylate reductionr2].

In the reduction of epidioxycyclopentene with azodicarbox- ylate only isomerization products could be isolated. Readily accessible peroxides of type (7) could simplify the prostaglan- din synthesis.

General Reduction Method

To a 50ml, round-bottom flask, provided with magnetic spinbar, are charged 5 mmol of the endoperoxide to be reduced and 15 mmol dipotassium azodicarboxylate in 10ml absolute methanol. While stirring magnetically and cooling by means of an ice bath, a solution of 30mmol acetic acid in 3ml absolute methanol is added dropwise within 30 min. After stirring for 3 h at 30"C, the solvent is rotoevaporated (0"C/10 torr), and the residue taken up in 20ml HzO and extracted twice with 20ml CHZCI2. The combined CH2C12 extracts are washed once with saturated aqueous NaHC03 solution, dried over anhydrous MgS04 and rotoevaporated (O0C/l 0 torr). The crude product is purified by recrystallization.

Received: August 1, 1977 [Z 808 I€] German version: Angew. Chem. 89,762 (1977)

CAS Registry numbers:

(6 1. 63797-42-2; 1,4-dihydro-l,4-dimethyl-l,4-epidioxynaphthalene, 35461 - 84-8; dipotassium azodicarboxylate, 491 0-62-7

(1 1, 592-57-4; (21,6671-70-1; ( 3 ) , 280-53-5; (4), 5718-73-0; (51, 59476-71-0;

r11

PI r31

~ 4 1 151

[61 [71

181

W Adam, Chem.-Ztg. 99, 142 (1975); Angew. Chem. 86, 683 (1974); Angew. Chem. Int. Ed. Engl. 13, 619 (1974). H. 0. Honse: Modern Synthetic Reactions. W. A. Benjamin, Menlo Park, Cal., 1972. (2): yield 41 %, m.p. 85-86°C; C. Kuneko, A. Sugimoto, S. Tanake, Synthesis 1974, 876: m.p. 88.5"C. J. W Hamersma, E. I. Snyder, J. Org. Chem. 30, 3985 (1965). The pure substance (by TLC) deteriorates on standing at room tempera- ture within a few days. It was, therefore, not possible to obtain elemental analytic data. 'H-NMR (CC14, TMS): 6=1.4-1.9 (m, 4H), 1.9-2.5 (m, 4H), 3.9 (rn, 2H); IR (CCL,): 2960, 2940, 2890, 2855, 1460, 1445, 1430, 1305, 1225, 1030, 950cm-'; MS: m/e=114 (71 %), 81 (loo), 67 (411, 57 (U), 43 (88) (P+ 1 =6.62 %, P+2=0.68 %, calc. 6.72 % and 0.59 %, resp.). H. Pager, J. Chem. SOC. 1938, 829. a) ( 5 ) : yield 90 %, m.p. 209-210°C (from methanol); 'H-NMR (CDCI,, TMS): 6=0.8-1.2 (CH3; 18H), 1.2-2.5 (CH, C H I , COCH3; 27H). 4.9 (m, I H), 5.15 (m, 2H); IR (CHCI,): 2955, 2870, 2800, 1730, 1440, 1365, 1350, 1250, 1025, 960, 900 cm- ' ; MS: m/e=472 (1 %); correct elemental analysis; b) (6): m.p. 93-94°C (from hexane); 'H-NMR (CDCI,, TMS): 6=1.60 (s, 6H), 1.70 (m, 2H), 2.30 (m, 2H), 7.28 (m,

1380, 1335, 1260, 1180, 1075cm-I; MS: m/e=190 (6%), 158 (93). 143 (loo), 128 (501, 115 (25) , 91 (36), 76 (251, 43 (62); correct elemental analysis. H. if. Wassrrmun, D. L. Larsen, J. Chem. SOC. Chem. Commun. 1972. 253.

4H); IR (CC14): 3075, 3030, 2990, 2940, 2890, 2850, 1590, 1470, 1460,

Angew. Chem. lnt. Ed. Engl. 16 (1977) No. 10 713