Reactions of protonated 1,3-diaza,-4,4-diphenyl-2-(methylthio)butadienes with isocyanides: preparation of imidazole and triazine derivatives

A New Access to 2-(Alkylamino)- and 2-(Arylamino)pyrroles by Addition of Isocyanides to Protonated 1-Azabutadienes

“…Most compounds of this type have been obtained by pecially in their formal [1ϩ4] cycloadditions to conjugated reaction of a nitrogen-two-carbon compound with an apdiaza and azathiadienes [7] or related iminium salts, [8Ϫ10] we propriate two-carbon unit (C 2 ϩC 2 ), e.g. base-promoted wondered whether it might be possible, under suitable concondensation of an α-amino ketone [13] or a conjugated ditions, to utilize the 1-azabutadiene system 1 in a similar azoalkene [14] with a nitrile containing an active methylene procedure.…”

“…About ten years ago, we found that the protonation of 1,3-diazabutadienes markedly increases their reactivity towards isocyanides. [8] By similar reasoning, we have explored the treatment of chloro imino sulfides or phenyl chlorodithioformate with aldimines, azines, or dimethylthioformamide in the presence of isocyanides as new routes to 4-aminoimidazolium [9] or 5-aminothiazolium [10] salts. Such useful synthetic methodologies involve imidoylor (thiocarbonyl)iminium chlorides as transient intermedi-Scheme 2.…”

Reactions of Isocyanides and Pyridinium Triflates − A Simple and Efficient Route to Imidazopyridinium Derivatives

“…[7] The cycloaddition step is reminiscent of the cyclocondensation reactions of isocyanides with protonated diazabutadienes, which represent efficient routes to mono heterocyclic compounds. [5,6] Such a [4 ϩ 1] cycloaddition was also proposed as the key step in the three-component condensation of amidines, aldehydes and isocyanides, leading to fused 3-aminoimidazoles. [4] Scheme 2.…”

Addition of isocyanides to ?-(methylthio)-benzylidenamidinium iodides: A surprising access to 2-(dialkylamino)imidazoles and 3,5-diamino-2H-pyrrolium salts

“…We previously reported the protonation of 1,3-diazabutadi- enes to yield imidazole or triazine derivatives by addition of isocyanides. In these cyclizations, isocyanides behave as nucleophilic or basic partners, involving a formal [1 ‫ם‬ 4] or [2 ‫ם‬ 4] cycloaddition reaction [7]. Similarly, we described the preparation of 4-amino-2-(methylthio)imidazolium salts through the combined action of isocyanides and benzaldimines on methyl chlorothioimidates.…”