Hydrochloric Acid → 2,5-Dimethylnaphtho[1,2-d]tellurazole

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Reaction Conditions

Reaction Steps

3-Chloro-5-methylnaphth[2,1-c][1,2,5]oxatellurazole (Example 4) (16.7 g=0.05 mole) was suspended in a mixture of tetrahydrofuran (THF, 200 ml) and methanol (40 ml) in a 500 ml three necked flask fitted with a nitrogen inlet, a condenser, and a powder addition funnel. Sodium borohydride was added under a nitrogen atmosphere and in small portions until the reaction mixture was a pale orange yellow. This required about 5 to 6 g. The powder addition funnel was then removed and replaced with a stopper. The reaction mixture was then cooled to 5° C. and acetic anhydride (5.1 g=0.05 mole) added slowly through the condenser. The reaction mixture transiently turned a bright orange. Concentrated hydrochloric acid (25 ml) was then added in one portion, the ice bath removed, and the mixture stirred to room temperature. As the reaction mixture warmed up, a crystalline deposit appeared and was collected by filtration. The crystalline deposit was washed with tetrahydrofuran until the filtrate was colorless and clear. The filtrate was then heated to boiling with a mixture of isopropanol (175 ml) and concentrated ammonium hydroxide (25 ml) and filtered hot with Celite®, the cooled filtrate was diluted with water until crystallization started. A first crop of pale yellow needles (5.06 g), m.p. 110°-112° C. was obtained. A further 1.65 g of product were obtained by two further extractions with the same solvent mixture, giving a total yield of 6.71 g=43.3% of theory. For analysis, the material was recrystallized from isopropanol. This did not change the melting point. Elemental analyses were in agreement with that expected for the structural formula.

Provenance & Evidence