Azodicarboxylates rearrangement

Treatment of 6-arylidenehydrazino-3-alkyl-5-nitrouracils 510 with etha-nolic KOH caused a benzylic acid type of rearrangement to give 511, which were alkylated to give 512, whose cyclization with diethyl azodicar-boxylate gave (80H1295) 513 by intramolecular cycloaddition through valence isomerization and then aromatization with diethyl azodicarboxylate (Scheme 107). 

The cycloadducts 257 of esters of azodicarboxylic acid to 2,7-dimethyloxepin undergo a spontaneous Claisen rearrangement to form the dihydrocyclopropapyridazines 258 (equation 139)132. Homofulvenes 259 (R1, R2 = HorMe) react with dimethyl azodicarboxylate to form rearranged adducts 260 (equation 140)133. 

Additionally, uracil 6-iminophosphorane, isocyanate, and o-methyl-e-caprolactim ether join to form the intensely yellow pyrimido[4 5 4,5] pyrimido[6,l-n]azepine (360), as shown in Scheme 130. Upon ring closure, methanol is spontaneously eliminated. Diethyl azodicarboxylate affords with the other components pyrimido[4,5-e][l,2,4]triazoline (361), which is closely related to the alkaloid isofervenuline. The imidazo[5, -/][ ,2,4]tria-zine (362) results in a known Michael-type rearrangement sequence by treatment with diethyl acetylenedicarboxylate (86JOC149, 86JOC2787) in this latter case, the Michael-type addition occurs much faster than the expected three-component reaction [93H(35)1055]. 

Formyl and 2-acetylfuran underwent an unusual reaction with ethyl azodicarboxylate to form adducts 285 and 286, respectively, as depicted in Equation (177) <1997T9313, 1999J(P1)73>. Computational studies of the reaction suggested an initial Diels-Alder reaction between the furan and azodicarboxylate, followed by rearrangement of the cycloadducts. A similar transformation was observed for the reaction between furfurals and 1,4-phthalazinedione in the presence of Pb(OAc)4, as shown in Equation (178) <20020L773>. 

When treated with benzoic acid in the presence of triphenylphosphine and diethyl azodicarboxylate, benzophenone oxime gave a high yield of f -benzoylbenzanilide (14), formed via rearrangement of the intermediate 0>benzoyloxime (15). Reaction of p>medioxyaGetophenone oxime with l,rsubstituted derivative (l ), whereas in the presence of allyl bromide... 

In total syntheses of 3-lactam antibiotics, the formation of 2-azetidinones is crucial. In a biomimetic synthesis, the N—C4 bond is best closed by the open chain hydroxamate (equation 48), because, depending on the different pATa values of the three potentially ionizable positions, only the ring-forming amide is ionized. 3-halohydroxamates are cyclized by base treatment, whereas 3-hydroxyhydroxamates cyclize via the Mitsunobu reaction (diethyl azodicarboxylate, PhsP). More highly substituted precursors yield isomeric 3-lactams after rearrangement. ... 

A combination of triphenylphosphine and diethyl azodicarboxylate (the Mitsunobu reagent) is useful for the rapid conversion of aromatic hydroxamic acids (211) to 0-(yV-arylcarbamyl)hydroxamates (212), products of the Lossen rearrangement. In some cases, a spontaneous second Lossen rearrangement occurs to give diarylureas (213), as shown in Scheme 33. The yields of (212) and (213) are 70-85%. The intermediacy of the phosphonium salts (214) has been suggested. 

Nucleophilic Attack at Other Atoms. A Lossen rearrangement occurs when aromatic hydroxamic acids are allowed to react with the triphenylphosphine-diethyl azodicarboxylate complex in the presence of ethanol, to give the hydroxamates (49). 

Ar)122 participate with increasing selectivity as 4it components in [4 + 2] cycloadditions, and much of this work has been reviewed.5-71-113 In selected instances, the expected bicyclodiazine products of the normal Diels-Alder reaction of cyclopentadienes and stable cyclopentadienones with 2ir participation of azodicarboxylates and diacyldiimides may rearrange to the corresponding 1,3,4-oxadiazines, the formal products of Diels-Alder 4ir participation of the azodicarboxylate or diacyldiimides with the dienes [Eq. (48)].123... 

A device which has been frequently used to produce a starting material with just one acyl group in place is to carry out a Beckmann rearrangement on an ortho-hydroxyaryl ketone, the Beckmann product cyclising in situ when the conditions are acidic a modern version of this is illustrated below." " An excellent route to mono-acylated precursors utilises mixed anhydrides.A very mild method for the dehydrative ring closure of or /io-hydroxyarylamino amides, employed in solid-supported benzoxazole syntheses, utilises typical Mitsunobu conditions - triphenyl-phosphine and diethyl azodicarboxylate." ... 

Coupling of oxindole 247 and the lithio derivative 248 (generated from the corresponding bromo compound) afforded ketone 246, which underwent the anticipated rearrangement to give the phalarine precursor 245 in 72% yield. Treatment of 245 with azodicarboxylate derivative 249 afforded adduct 250, which provided... 

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