Benzisoxazole synthesis

Nitration of a series of methyl-1,2-benzisoxazoles was studied by Tahkar and Bhawal using fuming nitric acid and sulfuric acid in acetic acid at 100 °C. 3-Methyl-1,2-benzisoxazole gave a mixture of 5-nitro- and 5,7-dinitro-3-methyl-l,2-benzisoxazole, with the 5-nitro isomer predominant. The product obtained from 3,5-dimethyl-1,2-benzisoxazole was the 4-nitro derivative and not the 7-nitro compound as proposed by Lindemann (26LA(449)63). The synthesis of the 7-nitro compound by an alternative method was used as structural proof. Two products were obtained from 3,6-dimethyl-l,2-benzisoxazole and these were the 5-nitro and 5,7-dinitro derivatives. 3,7-Dimethyl-l,2-benzisoxazole was converted into the 5-nitro derivative (Scheme 25) (77lJC(B)l06l). 

The synthesis of 3-acyl- and 3-aroyl-l,2-benzisoxazoles was accomplished by the desulfurization of (562). The dithioacetal (562) was prepared by the addition of the lithium salt of propenedithioacetal to an isocyanate with subsequent base cyclization (equation 61) (B-79MI41609). 

Pyrylium salts alkyl groups reactivity, 3, 662 aromaticity, 3, 640 arylammes from, 3, 657 benzenoid compounds from, 3, 656, 658 benzisoxazol-3-yl-synthesis, 6, 124 bicyclic... 

Based on this synthetic strategy an efficient method for the synthesis of 2,3-dihydro- 1,2-benzisoxazoles 137 and indazoles was elaborated [77a] (Scheme 57). 

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