Ring opening of 2,3-epoxy phenyl ketones upon reaction with nitric oxide

Epoxide rings of 2,3-epoxy phenyl ketones were cleaved by nitric oxide, affording regioselectively the C-3 ring-opened products, erythro-α-hydroxyl nitrates (2), in a highly syn-selective manner (isolated yield of the erythro products up to 91%). Products were identified by NMR, MS, and X-ray crystallography. The reaction is assumed to be initiated by NO₂, unlike a nucleophilic attack.     

Organolithium-induced enantioselective alkylative double ring-opening of epoxides: synthesis of enantioenriched unsaturated amino alcohols

The use of (−)-sparteine as an external chiral ligand in enantioselective organolithium-induced alkylative double ring-opening of dihydropyrrole epoxides and 7-azanorbornene-type epoxides gives unsaturated acyclic amino alcohols, and amino cyclohexenols in up to 87% ee.     

Synthesis of 6-hydroxymethyl-5,6-dihydro-4H-1,2-oxazines by one-pot-cyclization of dilithiated oximes with epibromohydrin

6-Hydroxymethyl-5,6-dihydro-4H-1,2-oxazines were regioselectively prepared by one-pot cyclization of dilithiated oximes with epibromohydrin.     

A new facile synthesis of shikalkin

A short and convergent approach for the synthesis of shikalkin （dl-shikonin） is presented. Stobbe reaction was employed to construct the aromatic skeleton 6. This is followed by a practical method to prepare the key epoxides 9 from aldehydes 8 in high yield. Finally, shikalkin is achieved by Grignard reaction and oxidation.     

Highly active, hexabutylguanidinium salt/zinc bromide binary catalyst for the coupling reaction of carbon dioxide and epoxides

An experimentally simple and inexpensive catalyst system based on hexabutylguanidinium/ZnBr₂ has been developed for the coupling of carbon dioxide and epoxides to form cyclic carbonates with significant catalytic activity under mild reaction conditions without using additional organic solvents (e.g. the turnover frequencies (TOF, h⁻¹) values as high as 6.6 × 10³ h⁻¹ for styrene oxide and 1.01 × 10⁴ h⁻¹ for epichlorohydrin). This catalyst system also offers the advantages of recyclability and reusability. Therefore, it is a very effective, environmentally benign, and simple catalytic process. The special steric and electrophilic characteristics of hexabutylguanidinium bromide ionic liquid result in the prominent performance of this novel catalyst system.     

Stereoselective epoxidation of 2-arylidene-1-indanones and 2-arylidene-1-benzosuberones

Summary Oxidation of the (E) and (Z) isomers of 2-arylidene-1-indanones (1) and 2-arylidene-1-benzosuberones (4) by alkaline hydrogen peroxide (methodi) afforded the spiroepoxidestrans-2a–g andtrans-5a–g from both isomers as sole products in high yields. On the other hand, dimethyldioxirane epoxidation(methodii) of the (E) isomers1a–g and4a–g gave the correspondingtrans spiroepoxides in good yields, whereas the (Z) isomers1a,c,e and4a,c,e led to thecis spiroepoxides in moderate yields. Dimethyldioxirane oxidation (methodii) of (Z)-1c and (Z)-4c,e gave diones3c and6c,e as by-products as well. Epoxidation of (Z)-1a,c,e and (Z)-4a,c,e bym-chloroperoxybenzoic acid (methodiii) resulted inca. 6:1 mixtures ofcis-2a,c,e andtrans-2a,c,e orcis-5a,c,e andtrans-5a,c,e spiroepoxides.Dedicated to Prof.W. Fleischhacker on the occasion of his 65^th birthday     

Mesoporous aluminosilicate promoted alcoholysis of epoxides

Mesoporous aluminosilicates efficiently catalyze the ring-opening of epoxides with a range of alcohols to give the corresponding β-alkoxyalcohols in high yields under extremely mild conditions and in short reaction times.     

Facile access to α-acyloxyamides via epoxide rearrangement/three-component domino reaction catalyzed by indium(III) chloride

A simple and efficient Passerini reaction of epoxides involving highly regioselective rearrangement of epoxide to aldehyde/three-component Passerini reaction catalyzed by indium(III) chloride is described. In the present protocol, epoxides served as wonderful substrates to furnish a library of α-acyloxyamides under mild reaction conditions in shorter reaction times and in good yields.     

First asymmetric total synthesis of aspinolide A

The first total synthesis of aspinolide A has been achieved using ring-closing metathesis as a key step. The stereogenic centers were generated by means of hydrolytic kinetic resolution (HKR) of racemic epoxides.     

Epoxidation of (Z)-3-Arylidene-1-thioflavanones

Summary.  Epoxidation of (Z)-3-arylidene-1-thioflavanones by sodium hypochlorite or alkaline hydrogen peroxide afforded diastereomeric mixtures of trans,cis- and trans,trans-epoxides. These were separated by silica gel column chromatography. Determination of the isomeric composition of the crude reaction products and structure elucidation of all new isolated epoxides were performed by ¹H and ¹³C NMR spectroscopy. Received November 10, 2000. Accepted December 19, 2000