Iodobenzene, amination

The carbonyiation of o-diiodobenzene with a primary amine affords the phthalimide 501 [355,356]. Carbonyiation of iodobenzene in the presence of (9-diaminobenzene (502) and DBU or 2,6-lutidine affords 2-phenylbenzimida-zole (503)[357, The carbonyiation of aryl iodides in the presence of pentaflnor-oaniline affords 2-arylbenzoxazoles directly, 2-Arylbenzoxazole is prepared indirectly by the carbonyiation of (9-aminophenol[358j. The optically active aryl or alkenyl oxazolinc 505 is prepared by the carbonyiation of the aryl or enol triflates in the presence of the opticaly active amino alcohol 504, followed by treatment with thionyl chloride[359]. 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

Buchwald-Hartwig amination of iodobenzene 92 with 2-benzyloxy-4-methyl-aniline 93 affords the diarylamine 94 in high yield (Scheme 32). In this case the Goldberg coupling gives poor yields. Oxidative cyclization of compound 94 using stoichiometric amounts of palladium(II) acetate in acetic acid under reflux leads to the carbazole 95, which by reductive debenzylation provides... 

For comparison, fluorous-phase-soluble Pd complexes are only 74-98% selective towards the trans product [168-170]. The isolated yields of the product approached 70% when a threefold excess of olefin to iodobenzene was used (Table 3) however, the percent yield decreased with the use of bromobenzene as expected since activation of bromine-carbon bonds is less favorable than iodo-carbon bonds. It was also possible to catalyze the reaction in the absence of additional triethylamine base (Table 3). In this case, the tertiary amines of the den-drimer most likely act as the base. The catalysts, in general, were fully recover-... 

Lin and Zhang reported the synthesis of l-hydroxy-3-methylcarbazole (23) starting from the nitro derivative 625 (578). This synthesis uses a Buchwald-Hartwig amination for the synthesis of the diphenylamine 628. After protection of the hydroxy group in the nitrophenol 625 as a benzyl ether, the nitro group was reduced to the corresponding amino derivative 627. Amination of 627 with iodobenzene under Buchwald-Hartwig conditions afforded the diarylamine 628. Palladium(ll)-mediated cyclization of 628 led to the carbazole derivative 629, albeit in low... 

Access to this type of compound is illustrated in Scheme 30 by the preparation of retro-sulfonamide tripeptide Boc-Pro-Leuijt[NH—S02]Gly-NH2(78). The two false termini used are the prochiral gem-diamino analogue of Leu and sulfoacetic acid. Amide to amine conversion according to Hofmann, carried out on the dipeptide Boc-Pro-Leu-NH2 (76) with iodobenzene l,l-bis(trifluoroacetate) gave the gem-diamino derivative 77. Coupling of the resulting gem-diamino derivative with methyl (chlorosulfonyl)acetate, followed by amida-tion of the intermediate methyl ester, afforded the desired pseudopeptide 78J1341 Full experimental details have not yet been reported. 

Exercise 14-19 The intervention of benzyne in the amination of chlorobenzene, bromobenzene, and iodobenzene with sodium amide in liquid ammonia originally was demonstrated by J. D. Roberts using 14C-labeled halobenzenes. Show explicitly how the use of a chlorobenzene-14C label could differentiate between amination by addition-elimination (Section 14-6B) versus amination by elimination-addition (benzyne mechanism). 

Other nucleophiles than amines which have been employed in the reaction are malononitrile and cyanoacetic ester anions. Both of these anions undergo a preliminary reaction with the aryl halide to form the C-aryl derivatives before they attack the ir-allylpalladium intermediate, so that diarylated products are formed (equation 31).86 Phenylmalononitrile anion reacts with iodobenzene and butadiene to give the same product in 70% yield. 

The advantage of the procedure introduced by Stork with bis(trifluoroacetoxy)iodobenzene (26) derives from the associated mild reaction conditions. Esters, thioesters, nitriles, secondary amides, amines, alcohols, halides, alkenes, and alkynes are all compatible with this transformation. 

Cyclic and acyclic enol derivatives 480 can be asymmetrically aziridinated with (A -tosylimino)iodobenzene 481 using a chiral copper catalyst prepared in situ from [Cu(MeCN)4]PF6 and the optically active ligand 479. Collapse of the aminal (i.e., 482) leads to the formation of enantiomerically enriched Q-amino carbonyl compounds 483, although ee s to date are modest <2000EJ0557>. Similarly, dienes can be selectively aziridinated using the chiral Mn-salen complex 484 to give vinyl aziridines 486 in scalemic form (Scheme 124) <2000TL7089>. 

Dipheny[amine (7) is prepared industrially either by heating aniline with aniline hydrochloride at 140 °C under pressure, or by heating aniline with phenol at 260 °C in the presence of zinc chloride. The most convenient laboratory synthesis uses the Ullmann reaction (Scheme 8.9) (see Chapter 10), in which acetanilide is refluxed with bromobenzene in the presence of potassium carbonate and copper powder in nitrobenzene solvent. Triphenylamine is similarly prepared from diphenylamine and iodobenzene. 

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