Selenol oxazole

Oxazoles. Activated isonitriles react with selenol esters in the presence of triethylamine and Cu20 at 25° to form oxazoles, presumably via a j8-keto isonitrile (equation I).1... 

Selenol esters also reacted with isonitrile (44 Scheme 13) at room temperature for 6-20 h in the presence of 1.5 equiv. of copper(I) oxide and triethylamine (or DBU) to give oxazole (45). The reaction presumably proceeds through an intermediate 3-ketoisonitrile (46), and copper(I) oxide functions as a reagent for complexation to the selenium moiety. 

To a mixture of 0.15 g selenol ester (0.41 mmol), 63 mg triethylamine (0.62 mmol), and 0.12 g methyl isocyanoacetate (1.21 mmol) in 5 mL anhydrous THF was added 92 mg anhydrous cuprous oxide (0.62 mmol). After being stirred at room temperature for 1 h, the reaction mixture was filtered through a pad of silica gel, which was eluted with EtOAc. The combined filtrate was concentrated in vacuo and the residue was purified by flash chromatography using EtOAc/hexane (1 3) as the eluent to afford 0.11 g oxazole ester as a colorless oil, in a yield of 73%. 

In 1980, Kozikowski reported that the combination of a selenol ester cf., 12) and copper(I) oxide also functioned as a suitable acylating agent in the Schdllkopf reaction. For example, ethyl isocyanoacetate (8) and selenol ester 12 were condensed in the presence of excess CU2O and triethylamine to provide oxazole 13 in 85% yield after 12 h at ambient temperature. This methodology subsequently found use in Weinreb s approach to amphimedine. ... 

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See also in sourсe #XX -- [ ]

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