Additional Nucleophile-Free FeCl₃-Catalyzed Green Deprotection of 2,4-Dimethoxyphenylmethyl-Protected Alcohols and Carboxylic Acids

Abstract

The deprotection of the methoxyphenylmethyl (MPM) ether and ester derivatives can be generally achieved by the combinatorial use of a catalytic Lewis acid and stoichiometric nucleophile. The deprotections of 2,4-dimethoxyphenylmethyl (DMPM)-protected alcohols and carboxylic acids were found to be effectively catalyzed by iron(III) chloride without any additional nucleophile to form the deprotected mother alcohols and carboxylic acids in excellent yields. Since the present deprotection proceeds via the self-assembling mechanism of the 2,4-DMPM protective group itself to give the hardly-soluble resorcinarene derivative as a precipitate, the rigorous purification process by silica-gel column chromatography was unnecessary and the sufficiently-pure alcohols and carboxylic acids were easily obtained in satisfactory yields after simple filtration.

Oxidative Functionalization of Catechol Derivatives Substituted with Electron-Withdrawing Groups

“…The electron-rich arenes can be useful nucleophiles, because the preliminary functionalization, which causes the production of wastes, is not required. 14,15) In our previous work 7) (Chart 1B), BF 3 •Et 2 O played a key role in switching the regioselectivity of the nucleophilic position on 3-methoxycarbonyl orthobenzoquinone (I) using an indole nucleophile. Acetic acid (AcOH) was produced during the PIDA-mediated oxidation of 1a.…”

Unified Total Synthesis of Pentacyclic Stemoamide-type Alkaloids

“…The ideal synthetic approach to these pentacyclic natural products would be a building block strategy combining four five-membered rings through three coupling events . The first coupling reaction between 8 and 9 provides tricyclic stemoamide ( 1 ) as a common intermediate. , Whereas the lactone-selective nucleophilic addition of lactone 10 to stemoamide ( 1 ) gives tetracyclic saxorumamide ( 2 ), the addition of lactone 11 would give protostemonamide ( 3 ). The subsequent lactam-selective nucleophilic addition of 10 would provide pentacyclic stemocochinin ( 4 ) and protostemonine ( 5 ).…”