The Newman-Kwart rearrangement is a reaction that converts a phenol to a thiophenol by forming a phenolic thiocarbamate with two alkyl groups (methyl) on the nitrogen. This is acheived by reacting dimethylthiocarbomyl chloride with sodium phenoxide and then heating it:
(picture credit. For their seminal publication, see Newman et al. mentioned below.)
In extension to this, Majetich et al. report alkyl isothiocyanates are able to react with saturated alkoxides to form sodium carbonimidothioate salts. The transition state depicted in the Newman rearrangement is strikingly similar to the salt produced from nucleophilic attack of the alkoxide on isothiocyanate where the sulfur atom bears the negative charge in both cases with the exception that in the rearrangement the nitrogen has a positive charge, but the sodium has the positive in the salt in the latter reaction. The authors illustrate this with the following scheme:
(Majetich et al., loc. cit.)
My questions are:
- Can a sodium carbonimidothioate salt undergo a similar rearrangement?
- What if we just add crown ethers to the reaction mixture. Will that remove the sodium and trigger the reaction? I am interested in the 2-mercaptopyridine which is cited as occurring readily at room temperature.
references
Newman, M. S. and Karnes, H. A. J. Org. Chem. 1966, 31, 3980-3984, doi 10.1021/jo01350a023.
Majetich, G.; Irvin, T. C.; Thompson, S. B. Tet. Lett. 2015, 56, 3326-3329, doi 10.1016/j.tetlet.2015.01.086.
