Dehydrogenation of zyxwvutsrqp 0-, S-, and N-Containing Heterocycles washed with water. Recrystallization from methanol was accompanied with considerable loss of product and no improvement of the melting point: 0.18 g (9O06): m p 167-70 "C; IR 3020,2920,1585, 1500,1470, 1438,1420,1270, 1230,1160,1120,1070,850,750,740,730,690 cm-'; H' NMR 6 4.17 zyxwvutsrqpo (s, 3 H), '7.62 (m, 14 H), 8.35 (s, 2 H). Anal. Calcd for Cj5H19N: C, 90.05: H, 5.74: N, 4.20. Found: C, 89.21, H, 5.79; N, 4.20. Pyrrole 15 (100 mg. 0.3 mmol) in benzene reacted immediately with N-phenylmaleimide (52 mg, 0.3 mmol) at room temperature. Evap- oration of benzenc and recrystallization of the product from methanol gave white needles of adduct 16: 100 mg (76Oh); m p 203-5 "C; IR 3050, 3020,2960,1760 Ish), 17~30,1490,1440,1380,1325,1190,1160,1150. 986, 860,750. SlCi, 690, 680 cm-'. 1,3-Diphenylnaphtho[2,3-c]thiophene (17a). zyxwvutsrq A mixture of 13 (0.2 g, 0.6 mmol) and phosphorus pentasulfide (0.26 g, 1.2 mmol) in pyridine (7 mL) was heated under nitrogen for 15 min. The cold re- action mixture furnished thiophene 17a as deep red needles: 0.19 g (95O)O); mp 194-5 "C (lit.'" mp 198-202 "C); IR 3040, 1590,1500, 1445, 1120.1030,870,765,7~50.740,690 cm-'. As reported,IO thiophene 17a did not add N-phenylmaleimide easily even on heating. 1,3-Diphenylnaphtho[2,3-c]furan (17b) and Adduct 18. zyxwvut A methanolic solution of 18 il g. 3 mmol in 15 mL) was heated to boiling on a steam bath. Sodium borohydride (0.1 g, 30 mmol) was added to the hot solution. and the reaction mixture was allowed to stand at room temperature for 20 min. Water was added and the resulting solid was collected and dried TIL showed the presence of unreacted 13 in the mixture; nevertheless. the mixture (0.3 g) was treated with hot acetic acid and furan 17b crystallized out as deep reddish-brown glistening plates The product was collected and washed with acetic acid: 0.15 g (5oo/obased on complete reduction of one carbonyl group); mp 140-3 "C (lit.l" mp 148-51 "CI; IR 1595,1470,1190,910,855,770, 740,690 cm-'. As reported by Cava and VanMeter,l0 furan 17b is unstable in or- ganic solvents and added N-phenylmaleimide instantaneously at room temperature to give adduct 18 (85%):mp 284-6 "C (lit.1omp 287-90 "C); IR 3060. 3000. 1775 (sh), 1700, 1600, 1500. 1450, 1380. 1345, 1315, 1285, 1200, 105<5, 1000, 960, 920, 890, 790. 770, 750, 730, dduct 18 (100 mg, 0.2 mmol) was dissolved in acetic acid-concentrated sulfuric acid (3:l mL) and heated on a steam bath. The yellow imide 19 pr'xipitated out in quantitative yield (95 mg): J. Org. Ch,em., Vol. zyx 44, No. 4, 197% 497 m p 378-80 "c; IR 1750, 1700,1430, 1360. 1160, 1120, 885, 750, 685 cm-I. Acknowledgment. The authors are thankful to Professors M. Z. Nazer and S. Sabri, University of Jordan, for the NMR spectra. Registry No.-la, 5435-97-2; lb, 7510-34-1; IC, 33315-71-8; Id, 53476-29-2; le, 53476-31-6; 2a, 6307-20-6;2b, 1056-77-5; 2c, 68630- 10-4; 2d, 68630-11-5; 2e, 68630-12-6; 3,643-79-8; exo- 4a, 68681-89-0; endo- 4a, 68681-90-3; 5a, 21815-18-9; 5b, 716-39-2; 8, 573-57-9; 9, 36724-38-6; 15, 68682-85-9; 16, 68630-15-9; 17a, 18929-58-3; 17b, 18929-57-2; 18, 18944-83-7; 19, 68630-16-0: N-phenylmaleimide, 941-69-5; maleic anhydride, 108-31-6; trans-dibenzoylethylene. 959-28-4;hydrazine, 302-01-2; methylamine, 7+-89-5, References and Notes 7149-49-7; 10, 68630-13-7; 12, 68630-14-8; 13, 18929-62-9; 11, (1) V. Mark, J. zyxwvut Am. Chem. SOC., 85, 1884 (1963): "Organic Syntheses", Collect. Vol. V, Wiley, New York, 1973, p 358. (2) M. S. Newman and zyxwv S. Blum, J. Am. Chem. Soc., 86, 5598 (1964). (3) F. Ramirez, 0. P. Madan, and C. P. Smith, J Org. Chem., 30, 2284 (4) The Chemistry of lsobenzofuran has been recently reviewed, M. J. Haddadin, (5) L. F. Fieser and M. J. Haddadin, Can. J. Chem., 43, 1599 (1965). (6) R. N. Warner, J. Am. Chem. SOC., 93, 2346 (1971). (7) R. F. Hudson and P. V. Clopard, Helv. Chim. Acta, 46, 2178 (1963). (8) "Dictionary of Organic Compounds", Vol. 4, Eryre and Spottiswoode, (9) M. P. Cava and R. I. Shirley, J. Am. Chem. Soc.. 82, 654 (1960). (1965). Heterocycles, 9, 865 (1978). London, 1965, p 2370. (10) M. P. Cava and J. P. VanMeter, J. Org. Chem., 34, 538 (1969). (11) M. J. Haddadin, N. C. Chelhot, and M. Pieridou, J. Org. Chem., 39, 3278 (1974); part of the title of this reference should read 3,4-b rather than (12) F. R. Japp and F. Klingemann, J. Chem. SOC., 57, 662 (1890). (13) C. S. Foots, S. Wexler, W. Ando, and R. Higgins, J. Am. Chem. Soc.. 90, (14)IW. Ried and H. Boden, Eer., 89, 708 (1956). (15) M. 0. AbdeCRahman. M. A. Kira, and M. N. Tolba, Tetrahedron Lett., 3871 (16) R. E. Lutz. J. Am. Chem. SOC., 51, 3020 (1939). (17) S. K. Kar and A. Kar, J. Org. Chem., 42, 390 (1977). (18) E. P. Kohler and C. F. H. Allen. J. Am. Chem. Soc., 50, 891 (19381. 2,3-~. 975 (1968). (1 968). Nickel Peroxide Dehydrogenation of Oxygen-, Sulfur-, and Nitrogen-Containing Heterocycles David L. Evans,l David K. Minster,2 Ulrich Jordis,3 Sidney M. He~ht,*~ Arthur L. Mazzu. Jr.. and A. I. Meyers* Deptrrtments of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02 139 and Colorado State Uniuersity, Fort Collins, Colorado 80521 Receiiwd August 31, 1978 Twenty-seven partially reduced 0-, S-, and N-containing heterocycles have been oxidized by the use of nickel peroxide. (Of particular interest were the conversions of several oxazolines to the corresponding oxazoles. a conver- sion apparently without precedent in the chemical literature, and the efficient oxidation of thiazolines to thiazoles. Since NiOa can effect thiazoline dehydrogenations in the presence of other functionalities. as may he judged by the successful oxidation of phleomycin A1 to bleomycin Az. the oxidant should be of utility for the preparation of natu- ral products containing thiazoles. Although the potential of nickel peroxide as an oxidant in organic synthesis has been recognized for a number of years,5 and a remark,able variety of transformations have been recorded,6 there have been few reported examples of the use of this reagent for heterocyclic dehydrogenations.7 We have recently utilized nickel peroxide for the oxidation of several A2-thiazolines to the corresponding thiazoles;8 in most cases, especially those involving thiazoline moieties that were part of relatively complex molecules, this oxidant was clearly the reagent of choice. Since the oxidation of partially reduced heterocycles IS a topic of continuing interest and investiga- 0022-3263/79/1944-0497$01.00/0 ti~n,~ we have studied the potential utility of NiO2 for other types of heterocyclic dehydrogenations. Of special concern in these studies was the oxidation of oxazolines to the corre- sponding 1,3-oxazoles, a conversion apparently without precedent in the chemical literature. Results and Discussion A series of eight substituted 4,5-dihydro-1,3-oxazoles were prepared as described10 and utilized in efforts to effect oxi- dation to the corresponding oxazoles. Although Barco et aLga have recently described the dehydrogenation of several isox- 0 1979 American Chemical Society