Isoxazolines synthesis

The selected examples by Studer et al. [159-161] reported the synthesis of two small discrete libraries of isoxazolines (eight compounds) and of amides derived from a Ugi 4CC reaction (ten compounds). The synthesis of the tagging silicon derivative and the scheme for isoxazoline synthesis are reported... 

FIGURE 7.20 Synthesis of tagging silicon derivative and scheme for isoxazoline synthesis. 

Table 10 2-Isoxazoline synthesis from benzonitrile oxide (223).

Figure 17.18. Isoxazoline synthesis via a 1,3-dipolar cyclo-addition.

The selected examples by Studer et al. [97-99] reported the synthesis of two small, discrete libraries of isoxazolines (eight compounds) and of amides derived from a Ugi 4CC reaction (10 compounds). The synthesis of the tagging silicon derivative and the scheme for isoxazoline synthesis are reported in Figure 16. A known silane [100] was coupled quantitatively with bromine in the fluorinated solvent FC-72 [101] and the tagging reagent was used to protect and label the allyl alcohols in THF. After the cycloaddition of the fluorinated dipolarophiles with the nitrile oxides, the protected isoxazolines were finally cleaved with HF/pyridine complex in ethyl ether. The scheme of the purification for each synthetic step is depicted in Figure 17. 

The commonly used reactive intermediates for isoxazoline synthesis are nitrile oxides, and two new ways of generating these... 

Fig. 14 Isoxazolines synthesis through 1,3-dipolar [3+2] cycloaddition reactions between ortho-quinone monoketals and benzonitrile oxides...

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