The Carbon–Nitrogen Triad Prototropic Tautomerism

Caution in the use of 2‐iminothiolane (Traut's reagent) as a cross‐linking agent for peptides. The formation ofN‐peptidyl‐2‐iminothiolanes with bombesin (BN) antagonist (d‐Trp6,Leu13‐ψ[CH2NH]‐Phe14)BN6−14andd‐Trp‐Gln‐Trp‐NH2

“…Enamines are normally stable only when the nitrogen is tertiary (contains no hydrogens), otherwise the imine form prevails (15). In addition, in their review of imine−enamine tautomerism, Shainyan & Mirskova (16) state that the presence of a thio‐group in the α‐position, such as an OR group (which exists as an iminoester), leads to a high content of the imino‐form.…”

Some new views on the tautomerisation mechanism

“…36 The results of qualitative and quantitative studies of the imine ± enamine tautomerism and, in particular, the hydrazone ± enehydrazine tautomerism, were comprehensively discussed in the review. 49 Shainyan and Mirskova 49 believed that the proton transfer in these processes occurs through an intermolecular mechanism. It was also noted that the hydrazone form is more stable in the absence of conjugation with an electron-withdrawing substituent.…”

Reactions of silylallyl-lithium or -potassium compounds with ButCN; synthesis and structures of [M{N(SiMe2R)C(But)(CH)3SiMe2But}] [M = Li(tmen), R = Me; or M = K, R = But], [Li{N(SiMe3)C(But)>>CCHC(SiMe3)(CH2)2C>>H2}(tmen)] and [{Li[NC(But)>>CHCHC(SiMe3)(CH2)2C>>H2]}4] (tmen = Me2NCH2CH2NMe2)

“…This equilibrium is known to be affected by the skeletal substituents and factors such as temperature and solvent. 8 In some cases, the enamine was shown to be preponderant; for example, for Bu n 2 C᎐ ᎐ CHNHSiEt 3 the imine was present only to the extent of 4%. 9 In each of the compounds 5a-5c the dominance of the dienamine is probably attributable to its greater conjugative stabilisation and the influence of the N-silyl substituents.…”

“…Water (0.15 g,8.33 mmol) was added with stirring to a solution of complex 2a(3.39 g, 7.14 mmol) in thf (25 cm 3 ) at room temperature. After further stirring for 30 min volatiles were removed in vacuo.…”