Introduction
The Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) is one of the most valuable reagents for activation of hydroxyl groups of carboxylic acids and alcohols.[
1
] It is a pale yellow crystalline solid which is stable at room temperature in closed containers under normal storage and handling conditions. CMPI is commercially available, but can be easily synthesized from 2-chloropyridine and methyliodide.[2a ]
[b ]
[c ]
[d ]
Scheme 1
It is widely used for the synthesis of esters,[
3
] lactones,[
4
] amides,[
5
] lactams,[
6
] and ketenes[
7
] from the corresponding carboxylic acids, as well for obtaining carbodiimides from thioureas[
8
] and thiocyanates from alcohols.[
9
] CMPI was introduced as an useful reagent for the synthesis of carboxylic esters by Teruaki Mukaiyama in 1975,[
10
] after that the miscellaneous N -alkyl-2-halopyridinium salts had been developed as activating agents.[
1
] Nowadays, several polymer-supported CMPI analogues have been used for the synthesis of esters and amides due to user-friendly purification procedures.[
11
] The reagent analogues are also valuable for peptide synthesis.[
12
]