The use of tin(IV) chloride to selectively cleave benzyl esters over benzyl ethers and benzyl amines

Benzyl esters are cleaved upon reaction with Sn[Cl.sub.4], resulting in isolation of the corresponding carboxylic acid. Importantly, benzyl ethers, amines, and amides do not undergo debenzylation under these conditions, nor do a variety of other common protecting groups for alcohols, thereby rendering Sn[Cl.sub.4] selective amongst Lewis acids. The scope, tolerance, and limitations of the strategy are demonstrated through the analysis of several multifunctional substrates, including those bearing Cbz groups. Key words: benzyl ester, deprotection, protecting group, chemoselective debenzylation. Les esters de benzyle sont clives en reagissant avec le Sn[Cl.sub.4], ce qui a pour effet d'isoler l'acide carboxylique correspondant. Il est important de noter que les ethers, amines et amides benzyliques ne subissent pas de debenzylation dans ces conditions ni ne forment d'autres groupes communs protecteurs des alcools, ce qui a pour effet de rendre l'acide de Lewis Sn[Cl.sub.4] selectif. La portee, la tolerance et les limites d'une telle methode sont prouvees par l'analyse de plusieurs substrats multifonctionnels, dont ceux porteurs de groupes carboxybenzyles. [Traduit par la Redaction] Mots-cles: ester de benzyle, deprotection, groupe protecteur, debenzylation chimioselective.
Introduction The use of protecting groups is essential to much of modern organic chemistry, despite admirable examples of natural product syntheses that lean to the contrary. (1) The benzyl protecting [...]