Unusual and Unexpected Reactivity of t-Butyl Dicarbonate (Boc₂O) with Alcohols in the Presence of Magnesium Perchlorate. A New and General Route to t-Butyl Ethers

Abstract

[reaction: see text] A new mild method for protecting alcohols as t-butyl ethers is reported. The reaction proceeds with Mg(ClO4)2 and Boc2O and shows general applicability. The deprotection of t-butyl ethers has also been revisited. Preliminary results indicate the CeCl3 x 7H2O/NaI system is a very suitable catalyst for their removal.

tert‐Butyl Ethers: Renaissance of an Alcohol Protecting Group. Facile Cleavage with Cerium(III) Chloride/Sodium Iodide

“…It is known that this system, in fact, is able to cleave the carbon-oxygen bond of ethers (R' À O À R) provided that the R framework bonded to oxygen is able to stabilize an incipient positive charge. [11] This should be the case with the tert-butyl ether [12] and, in fact, in our preliminary investigation [3] we succeeded in the deprotection of three tert-butyl ethers by using the hydrated CeCl 3 /NaI system. Herein we report a complete study on the cerium(III) chloride/NaI-promoted deprotection of tert-butyl ethers which involves evaluating of the effects of water and temperature on the reaction.…”

“…[1,2] We recently developed a new method to obtain tertbutyl ethers via an unusual reaction of alcohols with Boc 2 O in the presence of MgClO 4 . [3] The protocol was very efficiently applied to a large variety of alkyl and aryl substrates.…”

“…In our previous communication [3] on the formation of tert-butyl ethers, we reported some preliminary results on their deprotection accomplished with the CeCl 3 · 7 H 2 O/NaI system. It is known that this system, in fact, is able to cleave the carbon-oxygen bond of ethers (R' À O À R) provided that the R framework bonded to oxygen is able to stabilize an incipient positive charge.…”

Taking Up the Cudgels for Perchlorates: Uses and Applications in Organic Reactions under Mild Conditions

“…[45] This is a very important result since it represents the first general and simple methodology to afford tert-butyl ethers. The tert-butyl ether group is "one of the most underused alcohol protecting groups," although it is one of the few ethers stable under strongly basic conditions.…”

The First Simple Method of Protection of Hydroxy Compounds as their O-Boc Derivatives under Lewis Acid Catalysis

“…In fact, if protection of amines as Boc derivatives can be achieved in very good yields with zinc perchlorate as the catalyst, 15 aryl and alkyl tert-butyl ethers instead of the corresponding Boc derivative are obtained, when alcohols are allowed to react with magnesium perchlorate as the catalyst. 16 We screened many common Lewis acids in order to find one able to catalyze O-Boc alcohol formation, by using the reaction of octanol with Boc 2 O as sample reaction. 17 Perchlorates or triflates gave the exclusive formation of tert-butyl ether or a mixture of ether and carbonates, with the prevalence of the former.…”