Chemistry of 5-oxodihydroisoxazoles. Part 17.1 Acylation of 5-oxodihydroisoxazoles
作者:Rolf H. Prager、Jason A. Smith、Ben Weber、Craig M. Williams
DOI:10.1039/a700133i
日期:——
2-Unsubstituted isoxazol-5(4H)-ones and
-5(2H)-ones may be acylated by acid chlorides,
anhydrides or carboxylic acids in the presence of carbodiimides, to give
O- and N-acylated products. The solvent, the presence
of base and the temperature are found to alter the product ratios
dramatically, but the substituents present at C-3 have the greatest
effect. Aliphatic acid anhydrides and chlorides generally react at
nitrogen, but aroyl halides give significant proportions of
O-acylated products. Limited success in converting
O-aroyl to N-aroyl isoxazolones is reported.
Chemistry of 5-oxodihydroisoxazoles. Part 18.1 Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles
作者:Rolf H. Prager、Jason A. Smith、Ben Weber、Craig M. Williams
DOI:10.1039/a700134g
日期:——
N-Acylisoxazol-5-ones lose carbon dioxide under
photochemical and thermal conditions affording iminocarbenes which
undergo intramolecular cyclisation through the oxygen of the acyl group
to give oxazoles. Under photochemical conditions those acylisoxazolones
with electron withdrawing groups at C-4 usually give high yields of
oxazoles, while those with electron donating groups at C-4 give only
poor yields: the reverse is observed under thermal conditions.
A new synthesis of chiral aminoalkyloxazolecarboxylate esters from isoxazol-5(2H)-ones: the synthesis of almazoles A and B
作者:Jabbar Khalafy、Carina E. Svensson、Rolf H. Prager、Craig M. Williams
DOI:10.1016/s0040-4039(98)01014-4
日期:1998.7
2-(1-Aminoalkyl)oxazole-4 and 5-carboxylates are available, without detectable racemisation, by a sequence involving N-acylation of isoxazol-5(2H)one carboxylates with phthalimidoamino acids, photolysis of the acylated product, and hydrazinolysis. An application of the procedure to the synthesis of almazole A and B is described (C) 1998 Elsevier Science Ltd. All rights reserved.
The Synthesis of Some Chiral 2-Aminoalkyloxazole-4-carboxylates from Isoxazol-5(2H)-ones
作者:Matthew Cox、Rolf H. Prager、Carina E. Svensson
DOI:10.1071/ch03052
日期:——
Ethyl 4-methyl-5-oxo-2,5-dihydroisoxazole-3-carboxylate can be N-acylated by a number of natural and synthetic phthalimidylamino acids in the presence of carbodiimides. The N-acylated products form the corresponding oxazoles smoothly when irradiated at 300 nm in acetone. Removal of the phthalimido protecting group then gives 2-aminoalkyloxazole-4-carboxylate esters in good overall yields, and without