Synthesis of 3‐Acyl‐1,2‐benzisoxazoles

Abstract

A convenient method for the synthesis of 3‐acyl‐1,2‐benzisoxazoles, which are unstable toward bases, is described. Base‐catalyzed cyclization of 2‐alkyl‐ and aryl‐1,3‐dithian‐2‐yl o‐chlorophenylketoximes 4a‐1 gave 3‐(2‐alkyl‐ and aryl‐1,3‐dithian‐2‐yl)‐1,2‐benzisoxazoles 8a‐1, which were converted into the corresponding 3‐acyl‐1,2‐benzisoxazoles 1a‐1.

Five‐Membered Heterocycles: 1,2‐Azoles. Part 2. Isoxazoles and Isothiazoles

“…b-Hydroxyoximes 135, bearing a phenyl group unsubstituted in the ortho positions, are converted into styrylbenzisoxazole 136 upon treatment with phosphoric acid [10]. The base cyclization of dithioacetal 137 followed by desulfurization leads to 3-acyl and 3-aroyl-1,2-benzisoxazoles (138) [240] (Scheme 9.53). 9.5.1.2 Formation of Bond 1-2 1,2-Benzisoxazoles can be obtained from 2-hydroxybenzophenone oximes by thermolysis, treatment with base or with dehydrating agents (e.g., sulfuric and phosphoric acid).…”

A Novel PPh3 Mediated One-Pot Method for Synthesis of 3-Aryl or Alkyl 1,2-Benzisoxazoles

“…Hence, great efforts have been made to synthesize 1,2-benzisoxazoles, driven in part by the expected biological activities. In general, the reported synthesis of 1,2-benzisoxazoles could be found utilizing five distinct approaches (Scheme ): (1) [3 + 2]-cycloaddition of in situ generated nitrile oxides to arynes; , (2) catalyzed cyclodehydration of 2-hydroxyaryl aldoximes and ketoximes; (3) catalyzed intramolecular nucleophilic substitution of oximes in the presence of strong bases; (4) palladium-catalyzed intermolecular [4 + 1]-annulation of N -phenoxy acetamide with aldehydes; (5) intramolecular cycloaddition of S N Ar products from fluorous oxime tags or polymer-bound oximes to o -fluoro-benzonitriles . Yet, some limitations and drawbacks of these approaches could still be found such as the requirement of 3–4 steps for most reported procedures, preparation of starting materials or a long reaction time, , formation of undesirable byproducts, , and some harsh reaction conditions such as a strong base in the substitution of aryl halides. ,, …”

Laboratory-Scale Synthesis of Nitriles by Catalysed Dehydration of Amides and Oximes under Flash Vacuum Pyrolysis (FVP) Conditions

“…Torr, 30 min) over 3A MS using work-up Method B provided a yellow solid which, after distillation, was identified as 2-cyanophenol (621 mg, 88%); mp 90-93°C (Lit 19. mp 97-98°C); spectroscopic data as above.FVP of salicylaldoxime (1001 mg, 7.3 mmol, 145°C, 400°C, 3.0 × 10 -2 Torr, 36 min) over WO 3 using work-up Method A gave 2-cyanophenol as a dark yellow solid (758 mg, 87%); mp 93-95°C (Lit 19. mp 97-98°C); spectroscopic data as above.…”