Isoxazoles 3-hydroxy- from

The method presented in this chapter allows the direct preparation of isoxazole derivatives from primary nitro compounds and dipolarophiles with harmless reagents in catalytic amount, avoiding stoichiometric reagents and drastic reaction conditions. Moreover, this procedure is compatible with most common functional groups, including hydroxy, carboxy, and ammonium since yields are in general satisfactory, the procedure can be profitably employed with preparative purposes and has been exploited by other authors for the preparation of useful intermediates (see Table 8.3). A... 

Cyclopent-2-en-l-one, 2-hydroxy-3-methyl-synthesis, 3, 693 Cyclopentenone, 4-methoxy-formation, 1, 423 Cyclopenthiazide as diuretic, 1, 174 Cyclopent[2,3-d]isoxazol-4-one structure, 6, 975 Cyclophane conformation, 2, 115 photoelectron spectroscopy, 2, 140 [2,2]Cyclophane conformation, 2, 115 Cyclophanes nomenclature, 1, 27 Cyclophosphamide as pharmaceutical, 1, 157 reviews, 1, 496 Cyclopiloselloidin synthesis, 3, 743 Cyclopolymerization heterocycle-forming, 1, 292-293 6H-Cyclopropa[5a,6a]pyrazolo[l,5-a]pyrimidine pyrazoles from, 5, 285 Cydopropabenzopyran synthesis, 3, 700 Cyclopropachromenes synthesis, 3, 671 Cyclopropa[c]dnnolines synthesis, 7, 597 Cyclopropanation by carbenes... 

Several reactions giving rise to hydroxy- and amino-isoxazoles have also been investigated. Thus the reaction of alkoxymethylene-cyanoacetates and hydroxylamine leading to 5-amino- or 5-hydroxy-isoxazoles proved to be rather useful.It is of particular interest that, by changing the reaction conditions, Bauer and Nambury succeeded in obtaining isomeric aminoisoxazolones (24 25 26). It is also possible to prepare isoxazol-3-ones from some /S-ketoesters. ... 

In 1909, Thiele and Landers reported the synthesis of p- (3-methoxy-isoxazol-5-yl)-propionic acid (77), from the corresponding chloride or bromide (76). In 1961, a similar reaction was reported for 3-chloro-5-arylisoxazoles, enabling the synthesis of 3-hydroxy-5-phenyl-... 

A somewhat related sequence leads to trilostane (111), a compound that inhibits the adrenal gland more specifically the agent blocks some of the metabolic responses elicited by the adrenal hormone ACTH in experimental animals. Reaction of the hydroxy-methylene derivative 108, obtained from testosterone, with hydroxylamine gives the corresponding isoxazole (109). Oxidation of the C-4,5 double bond by means... 

However, chromones react differently, because the phenolic hydroxy group in the ring-opened intermediate is unreactive. Thus, isoxazoles (264) result from the reaction with hydroxylamine, and a pyrazole is formed with hydrazine. y-Pyrones also give pyrazoles with hydrazine. 

The mother liquors were concentrated to dryness and the residue recrystallized from ether to give solid product. The latter was chromatographed on a column of silica gel in benzene solution, recrystallized from ethyl acetate and dried at 75°C for 20 h to give 17p-hydroxy-4,4,17a-trimethyl-androsta-2,5-dien[2,3-d]isoxazole. 

There was thus obtained 2.35 grams of 17a-ethynyl-17p-hydroxy-4-androsteno[2,3-d]isoxazole, MP 224.2°-226.8°C (corr.) when recrystallized from acetone [a]D25= +7.5 0.2° (in 95% ethanol) ultraviolet maximum at 286 nm (E=ll,300). 

Bicyclic A(0-Mti-homonucleoside analogues such as 591 were synthesized through 1,3-dipolar cycloaddition of an enantiopure 3-hydroxy-l-pyrroline A -oxide and protected allyl alcohol and subsequent introduction of thymine by a Mitsunobu reaction <2003T5231>. Furthermore, isoxazole, isoxazoline, and isoxazolidine analogues of (7-nucleo-sides such as 592-594 were synthesized by 1,3-dipolar cycloaddition of nitrile oxides and nitrones derived from uracil-5-carbaldehydes with suitable dipolarophiles <2003T4733, 2006T1494>. 

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