First total synthesis of cucurbitaxanthin A applying regioselective ring opening of tetrasubstituted epoxides

The synthesis of cucurbitaxanthin A 1 was accomplished via the C(15)-3,6-epoxides 7e and 7f prepared by regioselective ring opening of the 3-hydroxy-5,6-epoxides 6e and 6f.     

Solvent-free direct regioselective ring opening of epoxides with imidazoles

The reaction of different epoxides with commercially available imidazole at 60 °C leads to the formation of the corresponding 1-(β-hydroxyalkyl)imidazoles in a regioselective manner. When the reaction is applied to a chiral epoxide [(R)-styrene oxide], the expected chiral alcohol is isolated with the same enantiomeric excess. The use of benzimidazole as the heterocyclic component in the same process also allows the simple preparation of the corresponding 1-(β-hydroxyalkyl)benzimidazoles.     

A magnetic nanoparticle‐catalyzed regioselective ring opening of epoxides by aromatic amines

Sulfonic acid‐functionalized silica‐coated magnetic Fe₃O₄ nanoparticles were synthesized and applied as a green catalyst for an efficient and environmentally friendly ring opening of epoxides with aromatic amines in good to excellent yields with high chemoselectivity. Clean aminolysis of various aliphatic and aromatic epoxides in ethanol generates β‐hydroxyamines under mild reaction conditions. The synthesized acidic magnetic nanoparticles were recovered using a simple external magnet and successfully reused for five runs without any appreciable loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Environmentally benign and highly regioselective ring opening of epoxides accelerated by ultrasound irradiation

Regioselective ring opening of aliphatic and aromatic epoxides with nitrogen heterocycles such as indoles and imidazoles was accelerated using an ultrasonic technique as a green approach. An optimized procedure with the catalyst of choice, MCM-41, represents a real alternative to the conventional reaction protocols owing to the catalyst recyclability, simplicity, green conditions and time-saving aspects.     

Highly regioselective ring opening of epoxides with alcohols catalyzed by organotin phosphate condensates

Organotin phosphate condensates proved to catalyze the ring opening reaction of epoxides with alcohols in a highly regioselective manner.     

Total synthesis of capsanthin using lewis acid-promoted regio- and stereoselective rearrangement of tetrasubstituted epoxide.

The synthesis of capsanthin 1 was accomplished via the C15-cyclopentyl ketone 13 prepared by Lewis acid-promoted regio- and stereoselective rearrangement of the epoxide 12.     

Zirconyl nitrate mediated regioselective ring opening of epoxides and aziridines: an easy synthesis of β-nitrato-alcohols and -sulfonamides

Epoxides and aziridines are cleaved efficiently and regioselectively in the presence of zirconyl nitrate at room temperature to afford the corresponding β-nitrato-alcohols and -sulfonamides, respectively, in high yields.     

Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide

Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time.     

Catalyst-free regioselective ring opening of epoxides with aromatic amines in water and solvent-free conditions

Without using any catalysts, a variety of epoxides undergo ring-opening by aromatic amines to afford the corresponding 1,2-amino alcohols in high to excellent yields with good regioselectivity in the presence of water as solvent and under solvent-free conditions.     

Task specific ionic liquid as solvent,catalyst and reagent for regioselective ring opening of epoxides in water

Task specific ionic liquid as a novel and environmental eco-friendly green catalyst has been synthesized and used in the ring opening of epoxides under green conditions. This ionic liquids as solvent, catalyst and reagent afforded the corresponding thiocyanohydrins and azidohydrines with good regioselectivity and very short reaction times. The desired thiocyanohydrins and azidohydrines in 83–93% isolated yields.     

Total synthesis of capsanthin and capsorubin using Lewis acid-promoted regio- and stereoselective rearrangement of tetrasubsutituted epoxides

The synthesis of capsanthin 1 and capsorubin 2 was accomplished via the C(15)-cyclopentyl ketone 6 prepared by Lewis acid-promoted regio- and stereoselective rearrangement of the epoxy dienal 5.     

Mild stereoselective formation of tri- and tetrasubstituted olefins by regioselective ring opening of 1,1-disubstituted vinyl oxiranes with dialkyl dithiophosphates

Presented in this Letter is a mild new method to stereoselectively ring open 1,1-disubstituted vinyl oxiranes using dialkyl dithiophosphate nucleophiles. This new reaction proceeds in toluene at room temperature to afford tri- and tetrasubstituted allylic alcohols with high Z-selectivity. The syn relationship between the alcohol and the newly incorporated dithiophosphate moiety presented an opportunity to evaluate the anionic hopping properties of the ring opening product. Treatment of the ring opening product with base results in a facile phosphate hopping followed by a selective thiolate 3-exo-trig instead of a 5-exo-tet cyclization.     

Fluoroboric acid adsorbed on silica gel catalyzed regioselective ring opening of epoxides with nitrogen heterocycles

Aryl epoxides can be opened in a regioselective and efficient manner with nitrogen heterocycles such as indoles, pyrroles and imidazoles in the presence of a catalytic amount of HBF₄-SiO₂ under mild conditions to afford the corresponding C-alkylated derivatives in good yields and with a high regioselectivity.     

Highly regioselective ring opening of epoxides using NaN3: a short and efficient synthesis of (−)-cytoxazone

A convenient and efficient synthesis of 1,2-azido alcohols has been achieved by regioselective ring opening of epoxides using NaN₃ and 4 Å molecular sieves in acetonitrile. The utility of this method has been demonstrated by achieving a short synthesis of (−)-cytoxazone in 48% overall yield.     

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

A reactant economizing process for the regioselective aminolysis of epoxides using equimolar quantities of reactants catalyzed by the double hydrogen bond donor N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is reported. Regioselectivity of the reaction is controlled by the electronic nature of the substituent on the styrene oxide, which has been substantiated on the basis of ¹³C NMR data and DFT calculations.     

A highly regio- and chemoselective synthesis of vicinal bromohydrins by ring opening of terminal epoxides with dibromoborane-dimethyl sulfide

Dibromoborane-dimethyl sulfide (BHBr₂-SMe₂) displays high degrees of chemo- and regioselectivity during the brominative cleavage of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydroborating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have been successfully accommodated during the epoxide opening process.     

An efficient protocol for regioselective ring opening of epoxides using sulfated tungstate: application in synthesis of active pharmaceutical ingredients atenolol,propranolol and ranolazine

Sulfated tungstate was found to be a new and highly efficient catalyst for opening of epoxide rings by amines to give β-amino alcohols with high regioselectivity. Various advantages associated with this novel and environmental friendly protocol include solvent-free conditions, short reaction times, high product yields, simple workup procedure and easy recovery and reusability of the catalyst. This protocol has been applied for the synthesis of active pharmaceutical ingredients atenolol, propranolol and ranolazine.     

H2TPP organocatalysis in mild and highly regioselective ring opening of epoxides to halo alcohols by means of halogen elements

We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H2TPP). Therefore a highly regioselective method for the synthesis of beta-haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H2TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present.     

A facile chemo and regioselective reductive opening of 1,2 epoxides via free radical reaction

a free reaction has been applied to several 1,2 epoxides; the regio and chemoselective reduction of the epoxy ring to afford secondary alcohols occours, in presence of NaI and nBu₃SnH in DME at 80·C, in rather good yield.