Ring closure of 2-substituted 3-(2-pyridylamino)acrylates (1 ) in phosphoryl chloride-polyphosphoric acid gives pyrido[l,2-a]pyrimidines (2). whereas (6-substituted 2-pyridyl) derivatives in Dowtherm A afford pyrido[l,Z-a]pyrimidines (2) and 1 A-naphthyridines (3). The 6-substituted pyrido[l,2-a]pyrimidines (2) can be converted thermally into 1.8-naphthyridines (3) by 1 -+ 3' N -+ C-acyl migration. Similar acyl migrations can be observed in other such systems.WE have reported that, in contrast to literature data,2 ethyl 1,4-dihydro-7-methy1-4-oxo-1,8-naphthyridine-3carboxylate (3b) is not formed directly from diethyl (6-methyl-2-pyridylaminomethylene)malonate (1 b) but by way of pyrido[l,2-a]pyrimidine (2b), and that compound ( 2b) is converted into (3b) by 1 -+ 3 N -+ Cacyl migration. We have also shown that, in addition to the pyrido[l,2-a]pyrimidines (2h and j),3 the 1,snaphthyridines (3h and j) can be prepared from the esters ( l h and j) .We now report further experiments conducted in order to establish (i) whether the behaviour of the acrylic acid derivatives (lb, h, and j) also applies to other acrylic acid derivatives (1), (ii) whether ring transformation also occurs with other pyrido[l,2-a]pyrimidines (2), and (iii) whether the acyl migration also occurs in other similar ring systems.Ring closure was carried out in Dowtherm A at 250 "C or in phosphoryl chloride-polyphosphoric acid at 130 "C. The results are summarized in Table 1. Pyrido[lJ2-a]pyrimidines and 1,s-naphthyridines were separated on the basis of the differences in solubilities and basicities. In both reactions the same results were obtained from either the Z-or the E-isomer [if R1 # C0,Et in (l)] indicating a fast isomerization under the given conditions.Ring transformations occurred in Dowtherm A at 250 "C and in liquid paraffin at 300-350 "C. The results are presented in Table 2. Isomerization failed with the pyridopyrimidines (2; R2 = H). At temperatures between 250 and 350 "C the startingsubstances were unaffected and at higher temperatures ( 3 5 0 4 0 0 "C) charring occurred. Isomerization was however successful for the compounds (2; R2 # H).The nitrile (2h) was prepared from the carboxamide * (2; R1 = CO-NH,, R2 = Me, R3 = H) with phosphoryl chloride. The pyridopyrimidines (2w, x, and y) 5a were prepared from the corresponding isopropylidene (2pyridylaminomethylene) malonat es .5a The pyridopyrimidine (2aa) was prepared from 2-amino-6-methyl-7 Tables 3 and 4 and Figures 1 and 2 are available as Supplementary Publication No. SUP 21970 (5 pp.

New types of bronchodilator agents, bi- and tricyclic nitrogen bridgehead compounds with a pyrimidin-4(3H)-one ring, were synthesized and evaluated for bronchodilator activity against serotonin-, histamine-, and acetylcholine-induced spasms in the guinea pig Konzett-Rössler test. The structure-activity relationships are discussed. The effects of some bi- and tricyclic derivatives on the human bronchus were also investigated. The homologous tricyclic compounds 68 and 69 were tested on isolated guinea pig ileum and trachea, and the effects of compound 69 were investigated in pilocarpine-treated dogs. Azepino[2,1-b]quinazoline (69; CHINOIN-1289) was selected for further biochemical and clinical investigations.

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In protic media, cyclic propargylamine N‐oxides 1 undergo solvent‐dependent competitive rearrangements leading to enamino aldehydes 5, acrylamides 3, and secondary amines 4. The ratios of the products are evaluated and the possible mechanism of the competing reactions is interpreted by reaction kinetics studies and ab initio calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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