Spectroscopic Evidence for the Structure of Isoxazolines and the

Spectroscopic Evidence for the Structure of Isoxazolines and the Mechanism of their Formation1,2. R. Percy Barnes, Gladys Estelle Pinkney, George McK ...
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NOTES

2 76 NH .H C 1 (EtO)&HCHIVH-XOOEt

1701.

nitrogen attached to what had been the carbonyl carbon atom of the chalcone.

+ C6H5CH2C0Et

(7

S I

76

I

C_)-C=CH-C--\

CbHSCH2COEt I

0 -

In some runs, phenylacetamide, which can arise from the decomposition of ethyl phenyliminoacetate hydr~chloride,~ was also found in the distillate.

I'

'2

S

0 ,c1) -C=CH-C-

SH-----hT I11

ll

Experimental Ethyl ~-(~'-Ethoxy-P'-phenylethylideneamino)-P,p-di- We have now examined the infrared spectra of a number of isoxoazolines, their related isoxazoles, ethoxypropionate (I).-In a 500-ml. flask fitted with a Hershberg stirrer were placed 25 g. (0.122 mole) of ethyl and a pyrazole in the belief that additional informa(3,P-diethoxyalanate6 and 37 g. (0.175 mole) of ethyl phenyl- tion as to the structure of isoxazolines would iminoacetate hydrochloride' in 200 ml. of ethylene dichloride. The mixture usually became warm a t the start and thereby be obtained. X,.j-Diphenyl-, 3-p-bromophenyl-3-phenyl-,X was cooled in an ice-bath. The bath was then removed and stirring continued at room temperature for 24 hours. phenyl-3-p-bromophenylisoxazolines and their corThe ammonium chloride was filtered from the product, the responding isoxazoles all showed strong absorption solvent removed under reduced pressure, and the residue ~~ to the -C=N- grouping, but a t 5 . 8 attributable fractionated through a 12-cm. Vigreux column; b.p. 125127" (0.04 mrn.), yield 30 g. (70%). The product was a no absorption in the 2-9p region. In contrast, light yellow oil, soluble in ether and insoluble in 10% hydro- 3,5-diphenylpyrazole shows absorption a t 2 . 9 ~ chloric acid. owing to the presence of an -NH- grouping. These Anal. Calcd. for C19H2905N: N, 3.99; C$HaO, 51.28. findings confirm the assignment of structure I to Found: S (Kjeldahl), 4.01, 3.96, 3.95; C2H60 (Zeisel), the isoxazolines, and Barnes and Dodson were in 51.12, 50.80. error in assigning t o 3-p-bromophenyl-