Reaction of Arylglyoxals with Electron‐Rich Benzenes and π‐Excessive Heterocycles. Facile Synthesis of Heteroaryl α‐Acyloins

Mutual Influence of (Dimethylhydrazono)methyl Groups and α‐Hydroxy Ketone Moieties in Hetaryl Analogues of Unsymmetric Benzoins

“…Because of the activation of the heterocyclic ring by the hydrazonomethyl group, the reaction can be performed smoothly with less active phenylglyoxal hydrate at room temp., which was found to be impossible for the unsubstituted heterocycles. [1] As a result of the higher electron-donor ability of pyrrole, the corresponding benzoin 2a forms more rapidly. Scheme 1 The α-benzoins 2 thus obtained quantitatively isomerize to the corresponding β-isomers 3 in the presence of a base (Et 3 N), small amounts of benzoin oxidation products Ϫ the hetaryl benzil analogues 4 Ϫ forming in parallel through the action of atmospheric oxygen ( Table 1, Entries 1 and 2; Scheme 2).…”

“…We have previously examined the synthesis [1] and isomerization in basic media [2] of α-benzoins. Our interest is in the study of hetaryl analogues of benzoins in which the het(aryl) residues contain functionalities modifiable over a wide range.…”

Aminocatalytic Cross‐Coupling Approach via Iminium Ions to Different CC Bonds

“…However, the same reaction at 80 8C resulted in 14 in 62 % yield (experiment b). [20] Treatment of compound 14 (1 mmol) with 2 a (20 mol %) failed to generate corresponding 1,2-dione 8 a, even on heating to 80 8C for 24 h (experiment c).…”

Mass-spectral behavior and thermal stability of hetaryl analogs of unsymmetrical benzoins

“…Earlier during investigation of the isomerization of α-benzoins obtained by electrophilic hydroxymethylation of π-excessive heterocycles [15] we demonstrated differences in the 1 H NMR spectral characteristics of the α-and β-isomers [16]. In the present work we studied the differences in the mass spectral characteristics of the obtained isomeric benzoins.…”