Double Metal Cyanides as Efficient Solid Acid Catalysts for Synthesis of b-Amino Alcohols Under Solvent-Free Conditions L. Saikia J. K. Satyarthi R. Gonnade D. Srinivas P. Ratnasamy Received: 20 November 2007 / Accepted: 21 January 2008 / Published online: 12 February 2008 Ó Springer Science+Business Media, LLC 2008 Abstract A novel application of Fe–Zn double metal cyanide complexes as solid, acid catalysts for regioselec- tive synthesis of b-amino alcohols under solvent-free conditions via ring-opening of epoxides with amines is reported for the first time. The conversion of epoxides to b-amino alcohols is nearly 100%. In the reaction with styrene oxide, regioselective b-amino alcohol formation is higher with aromatic than with aliphatic amines. Strong Lewis acidic Zn 2+ ions in the catalyst are probably the active sites in this reaction. Keywords Double metal cyanide (DMC) Á Solid Lewis-acid catalyst Á b-Amino alcohols Á Regioselective ring-opening of epoxides Á Single crystal X-ray structure 1 Introduction Development of efficient and eco-friendly catalytic routes for stereo- and regio-selective ring-opening of epoxides is an emerging area of investigation in organic synthesis. The b-Amino alcohol moiety, obtained by ring opening of epoxides, is a main structural unit in a vast number of natu- rally occurring and synthetic molecules of pharmaceutical importance. Among several applications, b-amino alcohols are used as b-blockers, insecticidal agents, oxazolines and as chiral ligands in asymmetric synthesis [1–5]. They are synthesized by nucleophilic addition of amines to epoxides via opening of the epoxide ring (Scheme 1). The classical synthesis of b-amino alcohols is generally carried out with a large excess of the amines at elevated temperatures and in the presence of organic solvents. This method is not suitable for poorly nucleophilic amines since regioselectivity is low. A large number of promoters and catalyst system have been reported, e.g. sulfamic acid [6], Amberlyst-15 [7], metal amides, metal triflates [8], transition metal halides [9], ionic liquids [10], and Lewis acids [11]. However, all those required long reaction times, elevated temperatures, high pressures and stoichiometric amounts of catalyst. Bro¨nsted acidic SBA-15 functionalized with sulfonic acid and Lewis acidic Ti-MCM-41 catalyze the reaction at mild conditions yielding high conversion and product selectivity [12, 13]. Double metal cyanide complexes are used as catalysts in the manufacture of polyethers-polyols [14, 15]. They also catalyze the copolymerization of epoxides and CO 2 pro- ducing polycarbonates [16], reaction of cyclic carbonates with alcohols yielding dialkyl carbonates [17] and pro- duction of biodiesel/lubricants by alcoholysis of vegetable oils [18]. We, now, report, for the first time, their appli- cation as solid, Lewis-acid catalysts for nucleophilic ring- opening of epoxides with amines producing b-amino alcohols. A series of b-amino alcohols was synthesized under solvent-free conditions using this Lewis acid catalyst. 2 Experimental 2.1 Material Preparation and Characterization Fe–Zn double metal cyanide (DMC) catalysts were pre- pared [18] using K 4 Fe(CN) 6 Á 3H 2 O as a source of Fe, L. Saikia Á J. K. Satyarthi Á R. Gonnade Á D. Srinivas (&) Á P. Ratnasamy (&) National Chemical Laboratory, Pune 411 008, India e-mail: d.srinivas@ncl.res.in P. Ratnasamy e-mail: p.ratnasamy@ncl.res.in 123 Catal Lett (2008) 123:24–31 DOI 10.1007/s10562-008-9410-z