Cycloamination reaction

The oxime nitrogen can also participate in cycloamination reactions to give pyrroles. Thus, treatment of oxime esters such as 185 with Pd(Ph3P)4 readily affords 186 [129]. The pentafluorophenyl group is necessary for good results otherwise a Beckmann rearrangement can unfavorably enter the picture. The oxime stereochemistry makes no difference on the outcome of the reaction. In addition to 186, pyrroles 187 and 188 were also prepared in this study (among others) [129]. 

The intramolecular coplanar cycloamination reaction of 2-(4-pentynyl)-5-phenylpyrimidine afforded [Pg.126]

Concurrent with this disclosure, Rossi reports a similar protocol wherein 2-acyl-l-(phenylsulfonyl)-3-iodoindoles 189 undergo room temperature palladium-catalyzed coupling with terminal alkynes to afford the corresponding 3-alkynylindoles 190 <01S2477>. Subsequent treatment with ammonia in methanol leads to formation of the p-carbolines 191 through sequential addition/elimination/cycloamination reactions accompanied by loss of the A -phenylsulfonyl group. 

The fully aromatic system is not necessary for the intramolecular Diels-Alder reaction to take place. 3-Butynylthio-l,2,4-triazin-5(2//)-ones (166a) undergo intramolecular Diels-Alder reaction in competition with an intramolecular cycloamination process, providing 2,3-dihydrothieno[2,3-Z>]pyridin-6(7//)-ones (167) and l,3-thiazino[3,2-Z>]-l,2,4-triazin-3-ones (168). The Diels-Alder reaction probably proceeds via an alternative tautomer, (166b) or (166c) (Scheme 34) <88JHC1733, 88JOC5093>. 

The pyrazino[2,l-ft][l,3]thiazin-5-ium trifluoroacetate salt (319 X = S) was obtained from the protonated pyrazino derivative (318 X = S) by intramolecular cycloamination, which proceeded instead of the expected Diels-Alder reaction (see Section 8.25.2.6.9) <89T6519>. 

Pyrido[l,2-u]benzimidazoles are prepared by hypervalent iodine C-H cycloamination of N-aryl-2-aminopyridines (Scheme 49) (13T10739).The reaction tolerated both electron-donating (OMe, Me, f-Bu) and electron-withdrawing groups (halides, nitro) on the aniline. However, sterics appears to slow the reaction as the yields were poor (9-23%) with same functional groups when placed ortho rather than para. A number of substituents (Me, halides, esters, CF3) were also tolerated on the pyridine ring. Quinolines and isoquinolines also reacted smoothly under these conditions. 

The gold(l)-catalyzed cycloamination of y-allenyl sulfonamides as reference reaction allowed us to study the influence of the nuclearity of the catalysts on their catalytic performance. Interestingly, the C3-symmetric trinuclear complex was found to surpass its mono- and dinuclear congeners both in terms of activity and enantioselectivity (up to 95% ee) (Scheme 15.19). 

Onogi et al. (2012) carried out reaction of methyl (lR,2S,4R,5R)-2-amino-4,5-di-bromocyclohexanecarboxylate in presence of K COj and dimethylacetamide solvent (DMA) at 60°C for 0.5 h to give unstable intermediate methyl (lS,2R,4S,5R)-7-aza-5-bromo-bicyclo[2.2.1]heptane-2-carboxylate via intermolecular cycloamination, which further reacts at 140°C for 1.5 h to form methyl (lS,2R,4S,5S)-7-aza-5-hy-droxy-bicyclo[2.2.1]heptane-2-carboxylate as final product under microwave irradiation. In this acyloxylation reaction, imusual endo-selectivity occurs due to 7-az-abicyclo[2.2.1]heptane skeleton. 

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