Synthesis of New Vinyl Thiocyanates by [3,3] Sigmatropic Rearrangement of Isothiocyanates

Abstract

Keywords: Alkynes / Allenes / Dienes / Isothiocyanates / Rearrangements / ThiocyanatesPropargyl isothiocyanates 3 and buta-2,3-dienyl isothiocyanates 20 were prepared conventionally from amines and thiophosgene, or by a new, one-pot procedure using nucleophilic substitution to generate azides, which in turn served as the starting materials for a Staudinger reaction, followed by treatment of the resulting iminophosphoranes or iminophosphates with CS 2 . Equilibration, through a [3,3] sigmatropic rearrangement, of 3 and the allenyl thiocyanates 4 was established by flash vacuum pyrolysis or by thermolysis in solution. Even the reversible isomerization of the parent compounds 3f and 4f favors the allenyl thiocyanate. In the case of 20, an irreversible rearrangement reaction gave high yields of 2-thiocyanatobuta-1,3-dienes 21. A sequence of two [3,3] migration steps transformed 1,4-diisothiocyanatobut-2-ynes 3m and 3n into 2,3-dithiocyanatobuta-1,3-di-

Synthesis of N-unsubstituted 1,2,3-triazoles via a cascade including propargyl azides, allenyl azides, and triazafulvenes

“…The starting compounds 2w,bb, 55 and 2dd 56 were described in literature and prepared by simple treatment of the corresponding bromides or mesylates with sodium azide. Similarly, the azide 2v was available from the appropriate and known 57 mesylate, whereas 2x was synthesized from hexa-4,5-dien-2-yn-1-ol 58 and phosphorus tribromide followed by the reaction of the resulting propargyl bromide with sodium azide.…”

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

“…The 2-step protocol developed by Banert et al [ 27 ] was adopted for the synthesis of the sensors. Thus nucleophilic substitution of the bromine atoms of 1,3-bis[bromomethyl]-2,4,6-trimethylbenzene with sodium azide in DMSO afforded the corresponding bis-azide.…”

A novel selective synthesis of β-isothiocyanato ketones

“…We hypothesized that -unsaturated aldehydes and ketones could be selectively transformed into respective β-isothiocyanato carbonyl compounds 1 and 3 by the addition of HN 3 to give -azido aldehydes and ketones [22,23] followed by transformation of the azido group into an isothiocyanato group using a Staudinger/aza-Wittig sequence [24][25][26][27][28][29][30]. In our preliminary communication, an example of the application of this methodology has been described [31].…”