Polyphosphoric esters

Carboxy-l-methylvinyloxy)quinoxaline (54) cyclized to 8-methyl-107/-pyrano 3,2-/]quinoxalin-10-one (54a) (polyphosphoric ester, no details).864... 

A few scattered examples of hexahydro- and octahydro-l,3-diazocines have been reported, mainly in the context of studies on the effect of chain length on the cyclization of diamines. Reaction of the N- aryl-iV - aroyldiamines (194) with polyphosphoric ester gives the cyclic amidines (195) (77JCS(P2)2068). Yields of the diazocines (195 n =5) were about 40%, compared to 90% for the 1,3-diazepine (195 n =4). The basicities of the products decrease in the order of ring size 6 7>8 5, lower basicity reflecting non-planarity of the amidine system. 

The 7-oxotriazolopyrimidine 89 was prepared by cyclizing triazoly-laminomethylenemalonate (88) by the action of polyphosphoric ester (93MI2) or by treatment of [(triazolylamino)methylene]dioxanediones (90) with Na2C03 followed by saponification with HC1 (91USP5061799) (Scheme 19). 

Aliphatic iodo and ureido groups cyclize when the compound is stirred with silver(I) perchlorate in the absence of light. A similar result is obtained by stirring with either water and then potassium hydroxide or MCPBA in chloroform these procedures gave slightly lower yields. Fully aromatized 2-aryloxazolopyridines are prepared in hi yield by heating an acylamino-chloropyridine with trimethylsilyl polyphosphoric ester (PPSE). 

Eudistomidin A (11) and eudistomins H (7), I (8) and P (9) have been made (127, 128) by the Bischler-Napieralski (BN) reaction, a method used extensively by the Hino group. Appropriately substituted tryptamine was condensed with BOC-prolinoyl chloride, then treated under BN conditions (POCl3 or polyphosphoric ester (PPE)) to produce a 5,7-disubstituted eudistomin skeleton (163). Eudistomin I thus results when starting from tryptamine (Scheme 9, R = R = H), eudistomin H from 5-bromotryptamine (Scheme 9, R = Br, R = H), eudistomidin A from 5-bromo-7-hydroxytryptamine (Scheme 9, R = Br, R = tosylate) eudistomin P is obtained from the use of 6-bromo-5-methoxytryptamine. 

Thermal cydization of enaminones 542 gives pyrrolo[3,2-6]pyridines 543, which may be N-alkylated to give pyrrolo[3,2-b]pyridones 545. Alternatively, 542 may be A-methylated to give the new enaminones 544, which are cyclized in polyphosphoric ester (PPE) to the pyrrolopyridones 545 (R2 = Me), Scheme 147 (85JHC83 90JHC1201). 

In 1986, Rao et al. reported their total synthesis of lavendamycin in 17 steps (Scheme 16) (60). 7-Bromo-5,8-dimethoxyquinaldic acid (153), which was synthesized in 10 steps from 8-hydroxyquinoline, was condensed with j8-methyltryptophan (127) to furnish the amide 154. In contrast to Kende s cyclization with polyphosphoric ester, which resulted in a 31% yield (55,56),... 

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