Intramolecular hydration of nitriles coordinated to cobalt(III). Formation of five- and six-membered chelated amides

Gold Activation of Nitriles: Catalytic Hydration to Amides

“…Heteroaromatic nitriles were also found to participate in this reaction (Scheme 3). An excellent yield was obtained in the case of furan-2-carbonitrile (18). Moderate to good yields were observed with nitrogen-containing heteroaromatics (19)(20)(21)(22), probably due to N coordination to the gold center.…”

Intramolecular hydrolysis of glycinamide and glycine dipeptides coordinated to cobalt(III). I. Mercury(2+), hypochlorous acid, and base hydrolysis of cis-[Co(en)2Br(glyNHR)]2+ (R = H, CH2CO2C3H7, CH2CO2-) and properties of cis- and trans-[Co(en)2(OH2/OH)(glyNHR)]3+/2+ ions

“…Using these results the immediate products of base hydrolysis of [Co(en)2Br(glyNH2)]2+ were determined (see eq [3][4][5]. Following quenching to pH ~4 after 5rt/2 for bromide These data were then corrected for subsequent hydrolysis of the chelated amide (eq 4), and hydroxo amide (eq 5), using rate data given in the caption to Table III.…”

“…1 Products of reaction at pH 8.77 (pH stat control). 5 (supplementary material). When compared with those of the optically pure species produced in the Hg2+-catalyzed reaction, the rotations correspond to 68 ± 2% retention in the [Co(en)2(glyO)]2+ ion under the two sets of conditions (pH 3.77, 8.77 [0.07 M HP042']) and a similar value (71 ± 2%) for the [Co(en)2(glyglyOC3H7)]3+ product when allowance is made for the presence of 13% trans-[Co(en)2(OH2)-(glyglyOC3H7)]3+ (pH 3.77) or a similar amount of racemic chelated dipeptide from the trans-hydroxo ion at pH 8.77. Since it has been shown that cyclization under these conditions occurs with full retention of configuration, it is concluded that the cis-hydroxo ion produced in the base hydrolysis reaction is 70% optically pure.…”

“…The intramolecular counterpart of Scheme II, as given by Scheme III for the hydration of aminoacetonitrile, has been observed for amino acid esters,15,16 amides,17 and nitriles5, 18 where fiveand six-membered chelate rings result. For aminoacetonitrile, a rate enhancement of ~10u occurs at pH 7,5,18 and this is to be compared with an acceleration of 106 for the Scheme I counterpart. 4 AH* factors now become of great significance, and it seems that the large positive AS* change found in Scheme I, and presumably arising from desolvation of solvent OH' in the transition state, is now apparent in the metal-hydroxo reactant.…”

“…4 AH* factors now become of great significance, and it seems that the large positive AS* change found in Scheme I, and presumably arising from desolvation of solvent OH' in the transition state, is now apparent in the metal-hydroxo reactant. 5,18 For the amino acid ester15,16 and amide17 species, however, the intramolecular hydrolysis reaction has not been observed directly; it was required to occur from results of lsO-tracer '17 It has now been possible to isolate the cis-hydroxo and cis-aqua complexes containing glycinamide, glycylglycine, and isopropyl glycylglycinate and to study their subsequent cyclization over the pH range 0-14. This is the first time that metal-facilitated intramolecular hydrolysis of simple amides has been observed in the absence of other equilibrium processes, and the rate profiles as a function of pH, catalysis by buffers, and other mechanistic aspects are of some general significance.…”