Thiourea catalyzed aminolysis of epoxides under solvent free conditions. Electronic control of regioselective ring opening

Organocatalytic Asymmetric Reactions of Epoxides: Recent Progress

“…[3a] Besides water, [17a] azide, [16] anilines, [37] alkyl amines, [38] N-Boc protected sulfonamides [39] and carbamates [17b] have been employed in the catalytic kinetic resolution. In the field of organocatalysis, cornerstone research showed that achiral ureas [40] and thioureas [41] are able to promote the regioselective ringopeningr eaction of epoxides. In 2008, Schreinera nd co-authors developed ar egioselective alcoholysis of styrene oxides assisted by an organocatalytic system composed of two Brønsteda cids, N,N-bis-[3,5-bis-(trifluoromethyl)phenyl]-thiourea 24 and mandelic acid 25 (Scheme 11).…”

Highly Effective Opening of Epoxides with Aromatic Amines in Presence of β-Cyclodextrin in Water

“…These reactions are accompanied by poor regioselectivity and long reaction time. To avoid these drawbacks, other methods were reported recently, which involved the use of metal amides [5][6][7], metal triflates [8][9][10], metal halides [11][12][13][14], organobismuth triflate complex [15], copper(II) tetrafluoroborate [16], ionic liquid [17], phosphomolybdic acid-Al 2 O 3 [18], thiourea [19] and Hβ zeolite [20]. However, most of these methods involve the use of expensive reagents, air-and/or moisture-sensitive catalysts, hazardous organic solvents and suffering from poor regioselectivity.…”

Regioselective Ring Opening of Epoxides with Amines Using Silica-bonded S-sulfonic Acid under Solvent-free Conditions

“…There are some limitations to this classical approach such as the requirement of elevated reaction temperatures in the case of less reactive amines, lower reactivity for the sterically crowded amines/epoxides and poor regioselectivity of the epoxide ring opening. To overcome these problems, several activators and promoters have been tried and reported in the literature, including metal salts [5][6][7], metal amides [8,9], metal alkoxides [10,11], metal triflates [12][13][14], alumina [15], microwave assisted montmorillonite clay [16], ionic liquids [17], heteropolyacids [18], amberlist-15 [19], thiourea [20], trifluoroethanol [21], silica [22], zeolites [23], organobismuth triflate complex [24], sulphated zirconia and SZ/MCM-41 [25]. However, these methods suffer from one or more disadvantages such as long reaction times [26], elevated temperatures [4,27], high pressure [22a, 28], moderate yields [18], use of air and moisture sensitive catalysts, requirement of stoichiometric amounts of catalyst, and problems in the recovery of the catalysts [26].…”