1.3.5- oxadiazines

Oxadiazine insecticides are derivatives of oxadiazine. Indoxacarb is the only member of this class. It is used for control of a wide range of lepidopterous insects in corn, vegetables, and fruit. Its oral LD50 in rats is 1732 mg/kg. 

---

The reaction of 2-aminothiazole derivatives with the 1,3,5-oxadiazine 2,4.6-trione shown leads to biuret derivatives (126) (Scheme 83) (287). 

Phenyl-3,6-dihydro-l,3,4-oxadiazin-2-one (50) is a high temperature blowing agent used primarily for polycarbonates (qv). It is prepared by the reaction of a-hydroxyacetophenone and methyl carbazate (52), made from hydrazine and dimethyl carbonate (175) ... 

Oxadiazine, tetrahydro-conformation, 3, 1054 ring-chain tautomerism, 3, 1056... 

Oxadiazines herbicidal activity, 3, 1085 reactions with bases, 3, 1060 ring contraction, 3, 1065 ring opening, 3, 1061... 

Two Nitrogen Atoms and One Oxygen Atom Synthesis of 1,3,4-oxadiazines 98H(49)557. 

Dehydrogenation of piperidine derivative 329 with Hg(II)-EDTA reagent afforded a mixture of perhydropyrido[l,2-n]pyrimidin-2-one 330 and pyrido[],2-c][],2,5]oxadiazine 331 (99ZN(B)632). 

Hexahydropyiido[ 1,2-d -1,3,4-oxadiazines 212 may formally exist in three con-formers (Scheme 138) [99ACSA213]. However, according to simple Hartree-Fock calculations, the trans conformer 212c is the energetically preferred structure. 

Fully saturated and 5,6-dihydro-4//-l,2,5-oxadiazines 106 (X = O) have been reported (96MI3), whereas the 2H- and 4//-l,2,5-oxadiazines 107a and 107b are still unknown. 

The enthalpies ofall the annular tautomers of l,3,4-oxadiazin-5-ones 117 and -2-ones 118 were calculated using the MNDO method (88CB887). The results clearly indicated that in both cases the hydrazone-type tautomers 117a and 118a are the most stable, while the formation of the tautomer 118c is the least probable. 

Early studies on tautomerism of benzo-fused 1,3,4-oxadiazines (70CB331 76AHCS1, p. 79) suggested the predominance of the 2H tautomer 119a, which, however, easily tautomerizes to the 4H isomer 119b on treatment with sodium alkoxide (Scheme 31). 

A variety of 2H- (121, X = O) and 4H- (122, X = O) 1,3,5-oxadiazines has been studied and eharaeterized, whereas 2//-l,3,5-thiadiazines 121 (X = S), unlike the 4H isomers 122 (X = S), are uneommon. The most eommon type of tautomerie intereonversions for sueh systems is ring-ehain tautomerism. A few studies on substituent tautomerism have also been earried out however, no data on annular tautomerism have yet appeared in the literature. 

The 1,2,6-oxadiazine ring system is mueh less known. Some reports eoneeming heteroeyeles of this type are ineorreet, while others are unsubstantiated (96MI4). 

---