Benzamidoximes: structural, conformational and spectroscopic studies. I

A Convenient Synthesis and Cytotoxic Activity of 3-Aryl-5-Pentyl-1,2,4-Oxadiazoles From Carboxylic Acid Esters and Arylamidoximes Under Solvent-Free Conditions

“…A proposed reaction mechanism for the formation the 1,2,4-oxadiazole is outlined in scheme 2. Initially the removal of the acidic 37 proton of 1 with a suitable base create an anion at the oxygen atom which attacks the carbonyl carbon of 2 to furnish an unstable tetrahedral species I with subsequent loss of ethanol to give II. Then, this intermediate is cyclized to furnish III, suffering elimination of water by heating (intermediate IV and V) to produce 1,2,4-oxadiazole 3.…”

An easy synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from carboxylic acids and arylamidoximes mediated by ethyl chloroformate

“…Carboxylic acids 1a-f were obtained from commercial sources while 1g and arylamidoximes 4h-j were prepared following the procedures reported earlier. 9,11 Typical experimental procedure A suitable carboxylic acid 1a-f (1.6 mmol) was dissolved in dry CH 2 Cl 2 (8.0 mL) and placed in a round bottom flask followed by the addition of K 2 CO 3 (0.33g, 2.4 mmol) under stirring and kept as such for 30 min at room temperature. Later, ethyl chloroformate 2 (0.2 mL, 2.4 mmol) was added to the same flask and stirred for an additional 30 min.…”

Synthesis of 1,3‐thiazole and 1,2,4‐oxadiazole substituted spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones

“…The α-bromoacetophenones IVa-e and various aliphatic as well as aromatic acid chlorides VIIa-e were purchased from Aldrich or Lanchester chemical companies. The N-hydroxy phenylamidines XIa-c were synthesized as per the reported method [13][14]. Melting points are uncorrected.…”