Synthesis 2004(5): 692-700  
DOI: 10.1055/s-2004-815977
PAPER
© Georg Thieme Verlag Stuttgart · New York

Scope and Limitations of Lithium-Ethylenediamine-THF-Mediated Cleavage at the α-Position of Aromatics: Deprotection of Aryl Methyl Ethers and Benzyl Ethers under Mild Conditions

Takeyuki Shindo, Yasuaki Fukuyama, Takeshi Sugai*
Department of Chemistry, Keio University, 3-14-1, Hiyoshi, Yokohama 223-8522, Japan
e-Mail: sugai@chem.keio.ac.jp;
Further Information

Publication History

Received 28 November 2003
Publication Date:
16 February 2004 (online)

Abstract

The scope and limitation of lithium-ethylenediamine-THF-mediated reductive bond cleavage at the α-position of aromatics were examined. Very mild conditions such as lithium metal (5 equiv) and ethylenediamine (7 equiv) in oxygen-free THF were quite effective for the demethylation of aromatic ethers even at as low as -10 °C. Allyl benzyl ethers were also deprotected under these conditions with very little change of the allylic alcohol moiety. Through this study, 2,6-dimethylbenzyl (m-xylylmethyl, MXM) group was developed as an alternative of benzyl group, which is readily cleavable under the above mentioned reductive conditions.

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2,6-Dimethylbenzyl group is possible to be abbreviated as DMB, The DMB group, however, is already well know as 2,4-dimethoxybenzyl group. We propose here the MXM group (m-xylylmethyl) to avoid the confusion in future.