Systems containing Three Heteroatoms

The 1 -1,2,4-triazepine (200) has been prepared, in 90% yield, by the reaction between diphenylnitrilimine and tetrachlorocyclopropene.  

A recent report on the synthesis of l,3,4-benzotriazepin-5-ones (202), via the reaction of o-aminobenzoylhydrazine with isothiocyanates and subsequent treatment with DCCD, has now been shown to be in error. An unequivocal alternative synthesis has shown that the products are the oxadiazoles (201).  

4-benzoxadiazepine salt (204) has been simply prepared by treatment of the hydrazone (203) with perchloric acid in acetic anhydride. 

4-thiadiazepinethione (205) has been isolated as purple needles from the reaction of dehydrodithizone with diphenylcyclopropenethione.  

7-lactams , e.g. (206) and (207), which are easily functionalized via metallation at the position a. to the carbonyl, are important precursors in the synthesis of penems. The preparation of chiral (206) from 6-amino-penicillanic acid and of chiral (207) from 4-acetoxyazetidinone have been described/  

4-benzothiadiazepine (201 R = H, X = NCONH2), prepared by the reaction of o-thiocyanatoacetophenone with semicarbazide, decomposed at 200°C in diethylene glycol to give the benzisothiazole (202 R = H). Similarly, (201 R = NH2, X = O) gave (202 R = NH2) on heating with polyphosphoric acid. The l,3,5-thiadiazepine-4,6-diones (203) were formed in good yield as 2 1 adducts of trimethylsilyl cyanide and thiobenzoyl isocyanate. A new 

A number of substituted l,3,4-benzotriazepin-5-ones (208) have been synthesized both by the cyclodesulphurization of the thiosemicarbazides (207) and by the reaction of (209) with isothiocyanates in the presence of dicyclohexylcarbodi-imide (DCDD). ° The benzotriazepinethiones (211) were prepared via the acid-catalysed cyclization of (210)/  

A metalloid template has been used in the synthesis of some triazepinones and triazepinethiones thus, for example, the reaction of acyclic diamines with dimethylsilicon isocyanate gave (212) after its reaction with thiocarbonyl diimidazole and subsequent hydrolytic removal of the silicon template, (212) gave (213)/ Aminohydroxy-l,2,4-triazepines (214 R = H or Me) have been prepared in high yield by the addition of aminoguanidine to acrylonitrile and related unsaturated esters.Condensation of )8-keto-esters with 1,2-diamino-imidazoles gave mainly imidazotriazepinones, e.g. (215), but with jS-diketones O 

4-benzotriazepin-5-one (217) did not react with methyl iodide, dimethyl sulphate, or diazomethane, but with methyl fluorosulphonate it gave not the expected 1-methyl-derivative but the relatively stable quaternary salt (218). This underwent ring-contraction to form (219) on treatment with acid.  

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Table 3) are described in the literature although the rarer 1,3,2- and 1,5,2-isomers are only known as the fully oxidized tetraoxides. Oxadiazines (Table 4) of all six types are reported, four of the isomers having an extensive and well established chemistry. The 1,2,3-and 1,2,6-isomers have been reported, but there is no spectroscopic evidence to support either structure. All the six isomeric thiadiazines (Table 5) are known with only the 1,5,2-isomer being poorly described. In line with the oxadiazines and thiadiazines being the most well known ring systems containing three heteroatoms, they are also the most well reviewed to date. 

Miscellaneous other Systems containing Three Heteroatoms. - Catechol is converted into the 1,3,2-benzodioxathiolan (503) by the action of EtNSFj. The cyclic iminodiacyl peroxide (504) is obtained from the imino-compound MeN(COCl)2 and hydrogen peroxide. The hydroxamic acid HOCPh2-CONHOH reacts with carbonyldi-imidazole to yield the dioxazolone (505). The i.r. and Raman spectra of l,3-dimethyl-l,3-diaza-2-boracyclopentanes (506 R = Cl, Br, or NMc2) have been reported. The zwitterionic salt... 

There has been a slight decrease in the total number of papers and patents this year, due in particular to a slackening in the flood of patents concerned with benzo[l,4]diazepines and related systems that are of potential pharmacological value. However, interest in 1,2- and 1,3-diazepines and in oxepin chemistry continues to increase and there has been a welcome upswing in the number of papers concerned with systems containing three heteroatoms, although this is still an area with much unexplored territory. 

Systems Containing Three Heteroatoms 7.1 Triazepines.- Cyclisation of (56) was found to yield l-(4-... 

Other Systems containing Three Heteroatoms 266 Oxadiazoles 266... 

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