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Advances in Heterocylic Chemestry. Vol 10 - Boulton A.J.

Boulton A.J. Advances in Heterocylic Chemestry. Vol 10 - Academic Press, 1969. - 347 p.
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98 . H. Robinson, O. Gnoj, A. Mitchell, R. Wayne, E. Townley, P. Kabasa-kalian, E. P. Oliveto, andD. H. R. Barton, J. Am. Chem. Soc. 83,1771 (1961).
99 . H. Robinson, O. Gnoj, A. Mitchell, E. P. Oliveto, and D. H. R. Barton, Tetrahedron 21, 743 (1965).
'/ +
(101) (100)
yield. The hydroxamic acid function is considered to arise via carbon-carbon fission of an intermediate alkoxy radical and this is supported by the isolation from the same photolysis reaction mixture of two isomeric hydroxamic acids, shown to be epimeric at C-13. The suggested pathway for this ring expansion is shown in sequence 102 - 103. This formation of hydroxamic acids appears to be
O- -NO
perfectly general, but its use has so far been confined to the steroid field.
Taylor and Eckroth100 have recently investigated the mechanism of the acid-catalyzed conversion of o-nitrobenzoyldiazomethane (104) to iV-hydroxyisatin (105), discovered by Arndt et al.101 Labeling studies with 14C in the diazo carbon atom gave results which ruled out a Wolff rearrangement, as all the label appeared in the isatin C-2 position. The following mechanistic pathway (104 -> 105) is favored over an alternative one proposed earlier by Moore and Ahlstrom.102
Taylor and Bartulin103 have recently shown that anthranil (106) reacts with a variety of active methylene compounds to give quinoline
100 E. C. Taylor and D. R. Eckroth, Tetrahedron 20, 2059 (1964).
101 F. Arndt, B. Eistert, and W. Part ale, Ber. Deut. Chem. Ges. 60, 1364 (1927).
102 J. A. Moore and D. H. Ahlstrom, J. Org. Chem,. 26, 5254 (1961).
103 E. C. Taylor and J. Bartulin, Tetrahedron Letters p. 2337 (1967).
1-oxides in almost quantitative yield. In the reaction with dimethyl malonate, the hydroxamic acid (107) is produced in 80% yield and the following mechanism (106 -s- 107) is proposed.
+ CH2(C02CHah
IV. Characteristic Reactions
A. Thermal Decomposition
When heated at or about their melting points cyclic hydroxamic acids commonly decompose to give the corresponding lactams. Thus,
'N'' 'O
h 1
N' H
aspergillic acid (4) when heated with a little copper chromite over a free flame gave 32% deoxyaspergillic acid.16 A similar decomposition has been observed with 1-hydroxyuracil.104 The thermal decomposition of alicyclic hydroxamic acids during 2-4 hours at 220-240 in vacuo has been investigated by Di Maio and Tardella.105 Compounds 108, 109, and 110 gave the corresponding lactams by loss of oxygen, but particularly in the bicyclic series unsaturated and aromatic lactams were also formed, e.g., 110 -> 111, 112, and 96.
B. Oxidation and Reduction
Alicyclic hydroxamic acids undergo several specific oxidative cleavage reactions which may be of diagnostic or preparative value. In the pyrrolidine series compounds of type 66 have been oxidized with sodium hypobromite70 or with periodates106 to give y-nitroso acids (113). Ozonolvsis gives the corresponding -nitro acids.70 The related cyclic aldonitrones are also oxidized by periodate to nitroso acids, presumably via the hydroxamic acids.107 This periodate fission was used108 in the complex degradation of Jle-nitrones derived from aconitine.

Reduction of cyclic hydroxamic acids generally leads to lactams or the corresponding amines. Chemical methods have frequently been preferred to catalytic hydrogenation, probably because the choice of
104 W. Klotzcr, Monatsh. Chem. 95, 1729 (1964).
106 G. Di Maio and P. A. Tardolla, Gazz. Chim. Ital. 94, 590 (1964).
106 V. M. Clark, B. Sklarz, and Sir A. Todd, J. Chem. Soc. p. 2123 (1959).
107 A. K. Qureshi and B. Sklarz, J. Ch&m. Soc. C, 412 (1966).
8 p. w Bachelor, R. F. C. Brown, andG. Biichi, Tetrahedron Letters p. 1 (1960).
catalyst for the latter is critical. Thus, 1 -hydroxy-2-pyridone was inert to palladium catalysts,42,109 but hydrogenolysis to 2-pyridone occurred readily over Raney nickel in methanol.109 l-Hydroxy-2-pyridone also resisted the action of stannous chloride or ammonium sulfide,42 and chemical reduction of similar aromatic hydroxamic acids may require more powerful reagents such as red phosphorus and hydriodic acid,42 sodium dithionite in hot aqueous ethanol,39,110 or hydrazine.35 Reduction of aspergillic acid (4) to deoxyaspergillic acid has been achieved by pyrolytic deoxygenation, by heating-with red phosphorus and hydriodic acid in acetic acid, and by heating with
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