Pergamon Tetrahedron Letters 40 (1999) 1847-1850 TETRAHEDRON LETTERS Cs2CO 3 Promoted O-Alkylation of Alcohols for the Preparation of Mixed Alkyl Carbonates Feixia Chu, Eric E. Dueno, and Kyung Woon Jung* Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620-5250, U.S.A. and Drug Discovery Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida 33612-9497. U.S.A. Received 18 November 1998; revised 5 January 1999; accepted 7 January 1999 Abstract The presence of cesium carbonate and tetrabutylammonium iodide (TBAI) facilitated efficient O-alkylation of alcohols with alkyl halides, giving rise to the exclusive formation of mixed alkyl carbonates, The cesium effect was also examined comparatively with other alkali carbonates. © 1999 Elsevier Science Ltd. All rights reserved. Keywords: Cesium carbonate; TBAI; O-alkylation of alcohols; mixed alkyl carbonates Organic carbonates exhibit unique physical and chemical properties, accommodating a variety of applications. 1 In numerous organic syntheses, carbonates have been useful intermediates for functional group manipulations, 2 while also being utilized in everyday applications (e.g., dyes, fuel additives, and lubricating oils)) Regarding polymerization, organic carbonates have been used in industry 4 as well as in biological and medicinal fields. 5 Recent studies have demonstrated promise in medical applications of aliphatic carbonates, 6 necessitating efficient carbonate synthesis. Common methods leading to carbonates are categorized into alcoholysis of phosgene or its derivatives, 7 organic carbonate exchange, 8 carbon dioxide alkylation, 9 and inorganic carbonate alkylation. 10 Nonetheless, these methods lack in generality for the synthesis of mixed alkyl carbonates, prompting us to embark on carbonate synthesis by cesium promoted O-alkylation. In the presence of TBAI, 4-phenyl-l-butanol 1 was ligated to 1-bromobutane through a CO2 bridge derived from Cs2CO 3, resulting in the exclusive formation of carbonate 2 in excellent yield (Scheme A). Advantages of this methodology and its mechanistic insights are discussed in this report. Scheme A ~~ /~OH B r~ Cs2COa TBAI DMF, 93 °C, 21 h 1 2 (91%, exclusive) 0040-4039/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. Pll: S0040-4039(99)00084-2