[66270-36-8] · C5H6Cl4O2 · 2,2,2-Trichloro-t-butoxycarbonyl Chloride · (MW 239.91)
Alternate Name: TCBOC-Cl.
Physical Data: mp 30-32 °C; bp 77-81 °C/12 mmHg.
Form Supplied in: colorless solid; commercially available.
Handling, Storage, and Precautions: moisture sensitive.
As a protecting group for amines, the TCBOC group is stable to acid and base conditions normally used to remove Boc groups (e.g. TFA) or to hydrolyze methyl esters (NaOH-methanol).1 The TCBOC group is attached under standard Schotten-Baumann conditions (eq 2). In addition to the reductive conditions6 originally described for removal of the TCBOC group (eq 3), sodium-2-thiophenetellurolate7 and zinc-acetylacetone8 (neutral conditions) also deprotect in high yield. Nucleosides,2,8 indoles,7,9 indolines,7,10 and anilines7 have been N-protected with the TCBOC group.
The TCBOC group is useful as an alcohol protecting group (eq 4). Horner-Emmons reagent (3) is stable below 0 °C and can be used to prepare a-keto esters (eq 5).3 As an alcohol protecting group the TCBOC group is not stable to aqueous base,4 in contrast to its use as an amine protecting group.
Scott McN. Sieburth & Elena Doval Santos
State University of New York at Stony Brook, NY, USA