Hydroxylamine and Pseudoacyl Systems: Pseudo-oximes

Abstract

Unhindered furan pseudoacyl chlorides react with hydroxylamine and a carbonate base to form oxidized cyclic N-hydroxyiminoimides. Thus, 3-chloroisobenzofuran-1-one forms 3-hydroximinoisoindolin-1-one (4) C₈H₆N₂O₂. Molecules are nearly planar and E-secondary amides hydrogen-bond with oximes through N(H)···N 2.920 Å and O(H)···O 2.720 Å contacts, and form infinite chains. Mucochloryl chloride (2,3,4-trichlorodihydrofuran-1-one) forms a similar hydroxyiminoimide (5E)-3,4-dichloro-5-hydroxyiminopyrrol-2-one (6), C₄H₂Cl₂N₂O₂. However, opianic acid forms a mixture of mostly N-hydroxyphthalimide [6,7-dimethoxy-N-hydroxyisoindolin-1,3-dione (9)], C₁₀H₁₀N₂O₂, with small amounts of open oxime carboxylate [potassium 2,3-dimethoxy-6-(N-hydroxymethanoyl)benzoate (8) C₁₀H₁₀NO₅K], and 2,3-dimethoxyphthalimide (10), C₁₀H₉NO₄. These results suggest an intermediate pseudo-oxime, and such a derivative has been made in quantitative yield in a dehydration resistant arylpyran pseudoacyl system. 3-Chloro-4,4-dimethylisobenzopyran-1-one reacts with two equivalents of hydroxylamine and a carbonate base to form 2-hydroxy-3-(hydroxyamino)-4,4-dimethyl-3H-isoquinolin-1-one (14), C₁₁H₁₃N₂O₃, a pseudo-oxime. Pairs of pseudo-oximes form four hydrogen-bonds in two complementary sets, with N(H)···O 3.008 Å and O(H)···O 2.685 Å. Molecules are also linked in chains by hydrogen-bonds with O(H)···O 2.696 Å. These products have been characterized by spectroscopy and X-ray diffraction.

Graphical Abstract

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