Oxadiazolone

Nitrilimines (621) are another class of 1,3-dipoles which provide a useful entry into the pyrazole ring. They are often generated by cycloreversion (79AG(E)72l) of tetrazoles, triazolopyridines and oxadiazolones (79JOC2957) (Scheme 55). Pyrazolines of known stereochemistry, pyrazoles and indazoles (Section 4.04.3.1.1(iii)) have all been prepared from nitrilimines. 

Reactions of stable mesito- and duronitrile oxides with 1-chloroalkyl isocyanates R R2CC1NC0 (R1 = CF3, R2 = Ph, 4-MeC6H4 R1 = CC13, R2 = H) gave oxadiazolones 176. The double adducts are formed by the cycloaddition of one nitrile oxide molecule at the isocyanate C=N bond and the nucleophilic addition of the chloroalkyl moiety to a second nitrile oxide molecule (344). 

In Scheme 39, new pathways to fused [l,4]thiazines are shown. The oxadiazolone derivative with a mercapto-methyl side chain (308) was reported to react with maleic anhydride to the fused product 309 in high yield <1996M549>. The acetylene substituted triazole 310, when reacted with 2molarequiv of phenylisocyanate, afforded a polysubstituted triazolothiazine derivative 311 via a fairly complicated reaction pathway <1998CJC635>. 

In contrast to (74), compounds (75) are easily hydrolyzed to amidoximes. IV(4)-Alkylation of oxadiazolones (74) by oxiranes has been used for a synthesis of oxadiazines <75CBi9ll>. 

Photolysis as well as thermolysis (150°C, copper-catalyzed) of (79) results in quantitative loss of CO2 (Scheme 29). The 1,3-dipole (80) cyclizes to the benzimidazole (81) or is intercepted by dipolarophiles like benzonitrile or by an alcohol (Scheme 29) <68TL325>. Other oxadiazolones of type (79) fragment to CO2, a nitrile, a nitrene, and a carbene finally leading to a host of products <79JCS(P1)483>. 

Heating arylamidoximes with diketene yields the oxadiazoles (181). However, in the presence of a strong base, the oxadiazolones (182) are formed (Scheme 81) <82CPB336,82M78i>. 

N-acylamino acids does not appear to have been studied previously. In solution, N-acyl-N-nitroso-a-amino acids are moderately stable to weak bases, such as triethylamine or sodium carbonate, but are decomposed rapidly at 0° to expel nitrogen on addition of sodium hydroxide (43). For example, treatment of N-nitroso-N-benzoyl-D,L-pheny1-alanine LXIIb with an aqueous sodium hydroxide solution at 0 gives benzoic acid and 1-hydroxy-3-phenylpropanoic acid LXVa in a 93% yield. The facile base-catalysed formations of a-hydroxy acids LXV are a general reaction and probably occur by intramolecular attack as shown in LXII->LXIII->LXIV. Oxadiazolone LXIV can decompose by various possible pathways to give LXV among which the carbonium ion pathway is least likely. 

Dihydrooxadiazoles 106 have been syntheised in moderate to high diastereomeric excess by the addition of aromatic nitrile oxides across the C=N bond of the hydrazones 105. The N-N bond can subsequently be cleaved with formic acid, and the chiral auxiliary recycled <99H(50)995>. The oxadiazolone 108 was produced (56%) from the oxime 107 by heating it with phenyl isocyanate <99SC3889>. ... 

Hewawasam, P., Chen, X., Starrett, J. E., (Bristol-Myers Squibb) Amino acid derivatives of diaryl 1,3,4-oxadiazolone, W09938853. 

Carbonic acid derivatives were used in early work to put a hydroxy group on C-5.40,41 Ethyl chloroformate reacts with amidoximes to give a carbonate ester that loses a molecule of ethanol in the cyclization. The expected oxadiazolone (8) is a tautomer of the 5-hydroxy form (9) (see... 

Uses herbicide, rice, orchards, vine Trade names Ronstar (Rhone Poulenc) Type oxadiazolone... 

Diflubenzuron urea Diflufenican amide, pyridine Dikegulac-sodium (other) sorbose derivative Dimefuron oxadiazolone, urea Dimepiperate thiocarbamate, piperidine Dimethachlor amide... 

Oxadiazon heterocyclic nitrogen, oxadiazolone Oxadixyl oxazolidine, amide... 

On thermal decomposition 3-substituted-4-nitrophenyl-l,2,4-oxadiazolones-5 form 2-substituted-4-nitrobenzimidazoles (Scheme 2.48) [390-393],... 

Reaction of diazocine 190 (see Section II,A,3) with phosgene afforded the oxadiazolone derivative 191 (79CPB2608). As mentioned earlier (see Section II,B,1), annelated diazocine 51 accompanied 50 (R = R1 = H) as a product of the Schmidt reaction of 1,3-cyclohexanedione. It was postulated, on the basis of ring-opened hydrolysis products (see Section IV,D), that 51 arose from annelation of 50 (R = R1 = H). [A 1,4-diazo-cinedione and its annelation product were also obtained (89AHC185), but it was determined that in this case annelation occurred at the intermediate seven-membered p-ketolactam stage, not on the diazocine that followed.]... 

Synthesis, Insecticidal Activity, and Anticholinesterase Activity of Some Oxadiazolones... 

This report summarizes the synthesis, insecticidal activity, and anticholinesterase activity of some novel N-dihydrobenzo-furanyl oxadiazolones. The compounds were primarily aphicides with reduced activity on houseflies, corn earworms and two-spotted spider mites. Some of these gompounds were potent anticholineterases (I-. values 1-10x10 M) that were slowly reversible. There was little relationship between in vitro... 

The synthesis of these molecules can be broken down Into two parts. The first segment consisted of preparation of the dihydrobenzo-furanylhydrazines from which the oxadiazolones were eventually prepared. These hydrazines were prepared as follows the ap-... 

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