Potassium Carbonate → 3-(Pyridin-3-yloxy)-4,5-dihydroisoxazole

Participants

Reaction Conditions

Reaction Steps

3-(pyridin-3-yloxy)-4,5-dihydroisoxazole I-236a and I-236b were prepared in 3 steps according to the following procedures: racemic dihydroisoxazole I-161 (1.0 equiv) was dissolved in N,N-dimethylforamide (0.1 M). Copper iodide (1.0 equiv) was added followed by trimethylsilylacetylene (3.0 equiv) and N,N-diisopropyl ethylamine (2.0 equiv). Palladium tetrakis (15 mol %) was added and the reaction was sealed and heated in a microwave reactor at 100° C. for 1 h. The reaction was allowed to cool after which it was transferred to a separatory funnel with ethyl acetate and water. The organic layer was then washed with water and brine, dried over sodium sulfate, concentrated and purified by flash silica gel chromatography (gradient ethyl acetate/hexanes). The TMS group was then deprotected by dissolving this material in methanol (0.07 M) and adding potassium carbonate (3.0 equiv). After stirring for 4 h at room temperature, the reaction was transferred a separatory funnel with ethyl acetate and water. The organic layer was then washed with water and brine, dried over sodium sulfate, concentrated and purified by flash silica gel chromatography (gradient ethyl acetate/hexanes). The resulting alkyne was then converted to the desired triazole by first dissolving it in neat trimethyl silylazide (80 equiv), purging the reaction mixture with Argon and heating in a microwave reactor to 110° C. for 3 h. After an additional 4 h of heating the reaction was 60% complete by LC/MS analysis at which point it was concentrated and purified directly by flash silica gel chromatography (gradient methanol/methylene chloride) to provide the desired racemic triazole I-236. These compounds can be separated using chiral HPLC methods known in the art. For example, see chiral HPLC Method disclosed herein. [M+H]+=392.9 m/z. Activity: A

Provenance & Evidence