Dihydro-1,3,5-dioxazines

The conformational equilibrium (Fig. 23) for N,N-dimethyltetrahydro-1,3,5-oxadiazine (457) is suggested by a priori considerations similar to those discussed above (Section III,G,1) for the dihydro-1,3,5-dioxazine system to... 

N—S bond rupture was found to be competitive with loss of a hydrogen atom from the weak molecular ions of iV-alkanesulfonyl- and N-arenesulfonyl-dihydro-1,3,5-dioxazines 11276. Equation 31 summarizes the major common fragmentation paths, with postulated ion structures, as emerged from the occurrence of metastable ions, high-resolution mass measurements and deuterium labelling. 

This system has been prepared by (1) the traditional method with formaldehyde and primary amines (Equation 71), and (2) condensation of bis(trifluomethylsulfonylamino)methane and paraformaldehyde (Equation 72). The ready availability of the starting materials and the high yields that are usually achieved in the first method recommend it for the preparation of dihydro-1,3,5-dioxazines. 

Dihydro-1,3,5-dioxazines are the reaction/condensation products of primary amines with 3 mol of formaldehyde. Although they release a higher quantity of formaldehyde than, for example, 1,3-oxazolidines and are therefore more effective than other formaldehyde releasing compounds they are not of practical importance as microbicides because of their limited stability and very pungent odour. 

Die analoge Reaktion des aus Phenylglycin erhaltlichen 2-Oxo-5-phenyl-4-pyrrolidino-dihydro-l,3,4-dioxazins ergibt l-(2-Hydroxy-l-phenyl-ethyl)-2-methyl-piperidin und zeigt potentielle Anwendbarkeit in der asymmetrischen Synthese1. 

The cycloaddition of methyl 1,2-dihydro-1-pyridine carboxylate and A -benzoyl hydroxylamine in the presence of an oxidant (Et4N+I04 ) can lead to two possible regioisomeric cycloadducts. On standing, the cycloadduct rearranges to yield a new compound, shown by x-ray crystallography to be the pyrido[4,3-e]-l,4,2-dioxazine (11a). This compound can only have arisen from the rearrange-... 

Acid-catalyzed dehydration of A-(2-hydroxyethyl)-A-acylhydrazines 674 is a general route to 4,5-dihydro-l,3,-4-oxadiazines 675 (Scheme 292) <1964JOC668>. 4,2-Dioxazines 678 are prepared by di-O-alkylation of hydroxamic acids using 1,2-dihalides or 1,2-dimesylates 676 (Scheme 293) <1971JOC284>. 

Acylnitroso compounds are best recognized for their ability to participate as dependable 2ir components of Diels-Alder reactions with dienes, and these observations have found substantial application in the total synthesis of natural products (Chapter 3).81 However, Mackay and coworkers have detailed the isolation of 5,6-dihydro-1,4,2-dioxazine 9a (10%) from the reaction of acylnitroso 7a with cyclopentadiene [Eq. (39)]. ... 

Although this product may arise from the [3,3]-sigmatropic rearrangement of the oxazine 8a, the acylnitroso 7b provided 5,6-dihydro-1,4,2-dioxazine 9b in excellent yield without the apparent intermediacy of the oxazine 8b.82 These observations suggest the potentially useful 4tt participation of acylnitroso compounds in Diels-Alder reactions. 

CyclischeHydroximsaureester,z.B. 5,6-Dihydro-l,4,2-dioxazine,werdendurchAlkylierung von Hydroxamsauren mit 1,2-Dibrom-ethanen in Gegenwart von Kaliumcarbo-nat95 bzw. aus N-Hydroxy-phthalimiden mit Chlormethyl-oxiran liber die Zwischenstufe des N-(2,3-Epoxy-propyloxy)-phthalimids hergestellt96 z. B. ... 

I -Hydroxy-ethyl) -3-( 2-methoxycarbonyl-phenyl) -5,6-dihydro-1,4,2-dioxazin 100%... 

Of the possible 24 bicyclic ring systems, only five have been described (Table 3). Among them, pyrido[l,2- >][l,5,2]dioxazines were postulated as reactive intermediates in the reaction of 1,2-dihydro-l-hydroxy-2-oxopyridine-6-carboxy lie acid with phosgene <88JMcn> but they have never been isolated. 

The aryl ether structure of fluoxastrobin (72 2005, HEC Bayer CropScience) [159] combines a methoximino 5,6-dihydro-l,4,2-dioxazin-2-yl toxophore with an optimally adjusted side-chain bearing a 6-(2-chlorophenoxy)-5-fluoro-pyrimidin-4-yl-oxy moiety as an essentia] element. 

The synthesis of key intennediate 360 bearing unnsnal fragment of 5,6-dihydro-1,4,2-dioxazin was developed by Bayer in 2002. Synthesis started from... 

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