Studies on Some 2,1-Benzisoxazole Derivatives

Abstract

(4) indicates that they are in fact best represented by structure l a rather than structures of type lb. Similar considerations also appear to hold for an isothiazole derivative 2a (5) and for a benzo-1,2-thioxole derivative 2b (6). However, it is of interest to examine related compounds in which the central atom is incapable of valency shell expansion to determine to what extent their properties approach those of the 6a-thiathiophthenes 1. These should possibly exhibit valencytautomerism which has been proposed (7) to explain the properties of the thiathiophthenes. A suitable compound for examination is 7-acetyl-3-methyl-2,I-benzisoxazole (3a), which has a structure of the required potential symmetry for n.m.r. examination and possesses similar electronic and structural features to some benzo-1,2-dithiolium derivatives (8) of the thiathiophthene system.2-Nitroisophthaloyl chloride (4a) reacted with ethyl ethoxymagnesiummalonate to provide the tetracarboxylic ester 46. This was not isolated but provided, after acid hydrolysis, 2,6-diacetylnitrobenzene (4c). This method is reported to be the most satisfactory for the preparation of o-nitroacetophenones (9). When the nitro compound was reduced, using stannous chloride in hydrochloric acid, 7-acetyl-3-methyl-2, I-benzisoxazole (3a) and 2,6-diacetylaniline (4d) were S-S-S S-S SR UR R J&AR L R1 = H; R2 = Me; Z = NMe b R1, R2 = CH:C(OMe)-CH:CH; Z = 0 obtained after separation by chromatography. 2,6-Diacetylaniline (4d) was obtained as the sole product when the reaction was performed at a higher temperature.Although the 'H n.m.r. spectrum of the 2,lbenzisoxazole 3a in deuterochloroform solution at 0" to 20" gave only one peak, indicating that Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.245.55.244 on 05/12/18For personal use only.

The Preparation and Properties of Some 2,1-Benzisoxazole and 2,1-Benzisothiazole Derivatives

“…It was also of interest to compare the properties of such 7-acyl-2,1-benzisoxazoles (1) with the corresponding 7-thioacyl-2,l -benzisothiazoles (2) to determine the relative effects, if any, of the sulfur and oxygen atoms in the valency tautomerism of the compounds, since the compounds 2, more so than 1, parallel the structure of a benzo-l,2-dithiolium derivative (3) which demonstrates magnetic equivalence of substitaents on the 3-and thioacyl positions. These comparisons were frustrated in an earlier study (1) by the lability of an aliphatic thione substituent. i n this work therefore, studies were directed towards the synthesis of esters and amides possessing the required potential symmetry.…”

“…[Traduit par le journal] 2,l-Benzisoxazole (anthranil) derivatives, particularly certain 7-substituted compounds, are of interest in studies on valency tautomerism (1). The ease with which the process occurs, however, appears to depend in some measure on the solvent used (1,2).…”

“…The ease with which the process occurs, however, appears to depend in some measure on the solvent used (1,2). To obtain more information on these compounds we have therefore attempted the synthesis of some other 2,l-benzisoxazoles and studied their properties.…”

Vielseitige Farbstoffsynthesen durch mehrfache Kondensationsreaktionen von Acetylanilinen mit Perylenanhydriden

“…[eV] Die direkte Kondensation von 2,6-Diacetylanilin [16] mit PDA 11 in Chinolin mit Zinkacetat ergab eine komplexe Reaktionsmischung, aus der die Zielverbindung 16 in lediglich 5 % Ausbeute isoliert wurde. Die niedrigen Ausbeuten dieser Reaktion kçnnen erklärt werden durch a) die geringe Nucleophilie des Amins, b) die Selbstkondensation des Acetylanilins in einer Friedländer-Reaktion [17] und c) partielle Decarboxylierung.…”

“…Die Umlagerung und Aromatisierung von 1 zu 4-HQ-Naphthalin 2 verursacht eine ausgeprägte bathochrome Verschiebung zu einem Absorptionsmaximum von l max = 425 nm. Die Integration des Stickstoffatoms in das Gerüst des 3a-Aza-1,6-phenalendions führt zu einem Absorptionsmaximum von 5 bei l max = 415 nm mit einer starken Rotverschiebung (Dl = 80 nm) gegenüber A. Durch das erweiterte p-System verdoppelt sich der molare Extinktionskoeffizient (e (l415) = 27 000 m À1 cm À1 ) gegenüber dem von A (e (l335) = 12 500 m À1 cm À1 ) und 2 (e (l425) = 11 300 m À1 cm À1 [16] mit PDA 11 in Chinolin mit Zinkacetat ergab eine komplexe Reaktionsmischung, aus der die Zielverbindung 16 in lediglich 5 % Ausbeute isoliert wurde. Die niedrigen Ausbeuten dieser Reaktion kçnnen erklärt werden durch a) die geringe Nucleophilie des Amins, b) die Selbstkondensation des Acetylanilins in einer Friedländer-Reaktion [17] und c) partielle Decarboxylierung.…”