DOI: 10.1002/adsc.201000607 Effective Guanidine-Catalyzed Synthesis of Carbonate and Carbamate Derivatives from Propargyl Alcohols in Supercritical Carbon Dioxide Nicola Della Ca’, a Bartolo Gabriele, b Giuseppe Ruffolo, c Lucia Veltri, c Tito Zanetta, a and Mirco Costa a, * a Dipartimento di Chimica Organica e Industriale, Università di Parma, Parco Area delle Scienze 17A, 43124 Parma, Italy Fax: (+ 39)-0521-905-472; phone: (+ 39)-0521-905-414; e-mail: mirco.costa@unipr.it b Dipartimento di Scienze Farmaceutiche, Università della Calabria, 87036 Arcavacata di Rende, Cosenza, Italy c Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende, Cosenza, Italy Received: July 29, 2010; Revised: October 22, 2010 Supporting information for this article is available on the WWW under http ://dx.doi.org/10.1002/adsc.201000607. Abstract: The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the pres- ence of organic bases as catalysts have been exam- ined. Bicyclic guanidines are effective catalysts for the formation of a-methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or a-methyleneoxazolidinones are obtained in high yields and good selectivities in one-step starting from propargyl alcohols and an ex- ternal nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon diox- ide. Propargylic diols under the same reaction condi- tions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbon- ates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields. Keywords: carbon dioxide fixation; carboxylation; homogeneous catalysis; organocatalysis; supercritical fluids Introduction Carbon dioxide is an easily accessible and renewable source of carbon. Indeed, the synthesis of industrially important chemicals based on carbon dioxide has at- tracted a growing interest. Previous works have also shown that the use of scCO 2 as solvent in conjunction with efficient catalysts can strongly reduce the envi- ronmental impact of many processes. [1] CO 2 is non- toxic, non-flammable, abundant and cheap. Recent comprehensive reviews from Jessop [2] and Baiker [3] list a large number of different kinds of homogeneous and heterogenous catalytic reactions, respectively, in supercritical CO 2 . Carbonates and carbamates are important targets in organic synthesis. They find wide application as sol- vents, as effective protecting groups for alcohols and diols involved in important syntheses of biological compounds, in the preparation of industrial products, polymers, pharmaceuticals and agrochemicals. [4] Their synthesis has been classically achieved by processes involving the use of phosgene, an highly toxic pollu- tant. An alternative and very attractive route to the production of these heterocyclic derivatives consists in the direct incorporation of CO 2 into an organic substrate. Propargyl alcohols and amines can be advanta- geously used in combination with CO 2 as starting ma- terials for the synthesis of functionalized cyclic carbo- nates and carbamates. This strategy is based on the “in situ” formation of propargyl carbonate HC  CC(R 1 )OCO 2  or propargyl carbamate HC  CC(R 1 )N(R 2 )CO 2  anionic species. Methods based on the use of transition metals such as Ru, [5] Co, [6] Pd, [7] Cu, [8] Fe, [9] phosphines, [10] inorganic bases (K 2 CO 3 ) in the presence of crown ethers, [11] or organic bases such as DBU coupled to Ag salts [12] have been developed for the reaction of CO 2 with propargyl al- cohols. Several reaction media have been used, such as conventional polar aprotic solvents, scCO 2 and ionic liquids in the presence of copper metal salts. [13] We now report a new guanidine-catalyzed one-pot synthesis of cyclic carbonates or carbamates and ox- alkyl carbonates or carbamates through the direct in- Adv. Synth. Catal. 2011, 353, 133 – 146  2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 133 FULL PAPERS