OXINDOLE, 3-ACETYL

Another pathway has been shown to occur in tomato, where lAA-aspartate is also oxidized to oxIAA-aspartate but is then A-glycosylated to form the glucopyranosyl-P-1 -A-oxindole-3-acetyl-A-aspartate and glucopyranosyl-p-1 -4-glucopyranosyl- 3-1 -N-... 

Acetyl )thiooxindole may be prepared by fusing together thio-oxindole and A,A -diphenylacetamidine to give the anil (217), which affords the acetyl compound on alkaline hydrolysis.573 Acetylation and benzoylation of thiooxindole are possible by using mixtures of acetic anhydride and sodium acetate or benzoic anhydride and sodium benzoate, respectively.575... 

Reduction of2-nitrophenylacetic acids. The best method of preparing l-hydroxy-2-oxindole is the reduction of methyl 2-nitrophenylacetate (169) with zinc and ammonium chloride and immediate acetylation... 

Vincatine (mp 111-112°) gave a molecular ion at m/e 370, in agreement with a molecular formula of C22H30N2O3. The IR spectrum showed carbonyl absorptions at 1705 and 1735 cm-1 and the UV spectrum indicated the presence of a 2-oxindole. Four aromatic protons were observed in the PMR spectrum together with JV-methyl (3.20 ppm) and carbomethoxyl (3.62 ppm) groups. Lithium aluminum hydride reduction gave a diol 164 but acetylation of this compound gave only a monoacetyl derivative. The structure of vincatine (163) was deduced on the basis of a rationalization of the mass spectra of the parent compound and its various derivatives, particularly the ions at m/e 297, 211, 182, and 124 in the parent compound (Scheme 3) and the base peak at m/e 184 (165) in the mass spectrum of the diol. 

Similarly, Sakamoto and co-workers treated A-acetyl-3-oxindole (116) with prenol (117) in the presence of CSA forming in situ compound 118 which underwent Claisen rearrangement to a mixture of 2-ferf-prenylated and 2-prenylated 3-oxindoles 120 and 121 with 120 being the major product (Scheme 23) [105]. After 10 h, tert-prenylated compound 120 was the only product, pointing at the interconversion... 

The attempted total synthesis " of 6-hydroxy-2 -(2-methylpropyl)-3,3 -spiro-(tetrahydropyrrolidino)-oxindole (127), an alkaloid of the dried root bark of Eleagnus communis (Wolf willow, or silverberry), " resulted in the formation of the epimer (128), or a mixture of (127) and (128) (Scheme 14). The final product showed great similarity to, but was not identical with, the alkaloid (127) however, (127) and the synthetic material gave the same product on acetylation, the reaction conditions for which presumably allowed epimerization at C-2. ... 

The first example of direct enantioselective addition of a C—H bond to a ketone was reported by Shibata and co-workers in 2009 using the cationic Ir/ (S)-Hg-BINAP as the catalyst in the synthesis of a chiral 4-acetyl-3-hydroxy-3-methyl-2-oxindole with 72% ee. Recently, Yamamoto and co-workers developed a cationic Ir/(R,R)-Me-BIPAM catalyzed asymmetric intramolecular direct hydroarylation of a-keto amides 178 affording the chiral 3-substi-tuted 3-hydroxy-2-oxindoles 179 in high yields with complete regioselectivity and high enantioselectivity (84-98% ee). In their proposed reaction mechanism, the aryl iridium complex formed via C—H bond activation is coordinated with the two carbonyl groups of the amide (Scheme 5.65). 

After copper and palladium, rhodium is the third most important transition metal for the synthesis of the indole ring. For a 2007 review on this reaction, see Patil and Paiil [1], Some early examples (Scheme 1) are Alper s rhodium reaction of 2-aryl-2/7-azirines to give 2-styiylindoles (equation 1) [2], Watanabe s Rh-catalyzed Fischer indole synthesis (equation 2) [3], Ucciani s 3-methylindole synthesis via the hydroformylation of o-nitrostyrene (equation 3) [4], and Burst s preparation of 3-acetyl-2-hydrox-yindoles from the Rh-catalyzed decomposition and carbenoid aromatic C-H bond insertion (equation 4) [5]. Narasaka extended Alper s 2-aryl-2//-azirine reaction to a Rh(II)-catalyzed synthesis of 2,3-disubstituted indoles [6], and both Cenini [7] and Alper [8] stretched the deoxygenation of o-nitrostyrenes to give indoles. Burst s Rh-catalyzed decomposition of a-diazo carbonyl compounds was used by Bauban [9] and Jha [10] in the synthesis of substituted oxindoles. 

Rearrangements related to the Bartoli-indole synthesis have also been designed for the preparation of ortho-alkylated anilides and oxindoles from O-acetyl-JV-arylhydroxylamines. 

Scheme 14.9 Oxindole synthesis via the [3,3]-rearrangement of O-acetyl-iV-arylhydroxymines.

MethyM-acetyl-axmdol 21, 291. 5-MethyI-l-acetyl-oxindol 21, 261. 

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