APPLICATIONS OF PERCHLORATES IN ORGANIC SYNTHESIS. A NEW AND GENERAL ROUTE TO t-BUTYL ETHERS Giuseppe Bartoli, Marcella Bosco, Manuela Locatelli, Paolo Melchiorre and Letizia Sambri Dipartimento di Chimica Organica “A. Mangini”, v.le Risorgimento 4, Bologna, Italy letizia.sambri@unibo.it In the last few years, we were interested in the use of various metallic perchlorates as Lewis acid promoters in various organic transformations.1 In particular, perchlorate salts have shown a high ability to activate 1,3-dicarbonyl systems. We surprisingly found that anhydrous Mg(ClO4)2 promotes the reaction of alcohols with t-butyl dicarbonate (Boc2O) to give t-butyl ethers.2 This reaction appears extremely interesting, as it represents a potential solution to a longstanding problem in organic synthesis namely, t-butyl ether formation. The t-butyl ether in fact is “one of the most underused alcohol protecting groups”,3 although it is one of the few ethers stable under strongly basic conditions. We set up a new protocol for the synthesis of t-butyl ethers from a large variety of functionalized aromatic and aliphatic alcohols. Selective mono-protection of symmetric and asymmetric diols can also be achieved. At the same time, a convenient deprotection protocol was set up. In fact, t-butyl ethers were easily reconverted in the corresponding alcohols by simple treatment with the CeCl3/NaI system.4 Scheme 1. 1. Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth. Catal. 2005, 347, 33-38. and references herein cited. 2. Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Org. Lett. 2005, 7, 427-430. 3. Greene, T. W.; Wuts, P. G. M in Protective Groups in Organic Synthesis, Wiley, New York, 3rd Ed., 1999, pp. 65-67. 4. Bartoli, G.; Marcantoni, E.; Sambri, L. Synlett, 2003, 2101-2116.
APPLICATIONS OF PERCHLORATES IN ORGANIC SYNTHESIS. A NEW AND GENERAL ROUTE TO t-BUTYL ETHERS
BARTOLI, GIUSEPPE;BOSCO, MARCELLA;LOCATELLI, MANUELA;MELCHIORRE, PAOLO;SAMBRI, LETIZIA
2005
Abstract
APPLICATIONS OF PERCHLORATES IN ORGANIC SYNTHESIS. A NEW AND GENERAL ROUTE TO t-BUTYL ETHERS Giuseppe Bartoli, Marcella Bosco, Manuela Locatelli, Paolo Melchiorre and Letizia Sambri Dipartimento di Chimica Organica “A. Mangini”, v.le Risorgimento 4, Bologna, Italy letizia.sambri@unibo.it In the last few years, we were interested in the use of various metallic perchlorates as Lewis acid promoters in various organic transformations.1 In particular, perchlorate salts have shown a high ability to activate 1,3-dicarbonyl systems. We surprisingly found that anhydrous Mg(ClO4)2 promotes the reaction of alcohols with t-butyl dicarbonate (Boc2O) to give t-butyl ethers.2 This reaction appears extremely interesting, as it represents a potential solution to a longstanding problem in organic synthesis namely, t-butyl ether formation. The t-butyl ether in fact is “one of the most underused alcohol protecting groups”,3 although it is one of the few ethers stable under strongly basic conditions. We set up a new protocol for the synthesis of t-butyl ethers from a large variety of functionalized aromatic and aliphatic alcohols. Selective mono-protection of symmetric and asymmetric diols can also be achieved. At the same time, a convenient deprotection protocol was set up. In fact, t-butyl ethers were easily reconverted in the corresponding alcohols by simple treatment with the CeCl3/NaI system.4 Scheme 1. 1. Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth. Catal. 2005, 347, 33-38. and references herein cited. 2. Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Org. Lett. 2005, 7, 427-430. 3. Greene, T. W.; Wuts, P. G. M in Protective Groups in Organic Synthesis, Wiley, New York, 3rd Ed., 1999, pp. 65-67. 4. Bartoli, G.; Marcantoni, E.; Sambri, L. Synlett, 2003, 2101-2116.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
