Oljan Repic

1,3-Syn diastereoselective reduction of β-hydroxyketones utilizing alkoxydialkylboranes

Abstract Sodium borohydride reduction of β-hydroxyketones in presence of alkoxydialkylboranes 1–7 as complexing agents, produced 1,3- syn diols in at least 98:2 ratio. As illustrated with examples 8–17 this method is quite general and superior to those described in the literature.

ETHYL TRIFLUOROACETATE : A POWERFUL REAGENT FOR DIFFERENTIATING AMINO GROUPS

Abstract Selective protection of primary amines in the presence of secondary amines and monofunctionalization of symmetric primary and secondary diamines using ethyl trifluoroacetate is described. Effective differentiation of primary, secondary and tertiary alkyl-substituted primary amines from one another by ethyl trifluoroacetate acylation is also demonstrated. These results are explained on the basis of steric and electronic effects of the substrate amines.

A new, economical, practical and racemization-free method for the reductive removal of 2-oxazolidinones from N-acyloxazolidinones with sodium borohydride

Abstract A new, economical, practical and racemization-free method for the reductive removal of 2-oxazolidinones by a reduction of N-acyloxazolidinones with sodium borohydride in THF and water is described.

Mild and regioselective oxidative bromination of anilines using potassium bromide and sodium perborate

Abstract The selective monobromination of various deactivated anilines using potassium bromide and sodium perborate as oxidant has been achieved. The use of ammonium molybdate as catalyst accelerates the rate of reaction but is not essential to obtain good yields and high selectivities.

Large scale microwave-accelerated esterification of carboxylic acids with dimethyl carbonate

An environmentally friendly process for the esterification of carboxylic acids with dimethyl carbonate can be accelerated by employing a combined strategy: using 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the catalyst (chemical means) and microwave as the energy source (physical means). This approach provides synthetic advantages, niches, and upscalability.

Ultrasound in organic synthesis: cyclopropanation of olefins with zinc-diiodomethane

Abstract Activation of zinc with ultrasonic irradiation facilitates the Simmons-Smith reaction.

DABCO- and DBU-accelerated green chemistry for N-, O-, and S-benzylation with dibenzyl carbonate

Abstract An environmentally friendly process for the benzylation of nitrogen, oxygen, or sulfur atoms with dibenzyl carbonate has been developed. Catalytic amounts of DABCO or DBU can accelerate this ‘green’ alkylation.

Enantioselective acylation of β-aminoesters using penicillin G Acylase in organic solvents

Abstract The resolution of racemic β-aminoesters has been achieved through selective acylation catalyzed by Penicillin G Acylase (ChiroCLEC TM -EC). The method has been optimized using three different phenylacetyl donors, and the effect of solvents on the rate of reaction is described. The efficiency of our method is illustrated by the synthesis of five different β-aminoesters with high enantiomeric purities.

ASYMMETRIC SYNTHESIS OF 3,5-DIHYDROXY-6(E)-HEPTENOATE-CONTAINING HMG-COA REDUCTASE INHIBITORS

Abstract A ‘one-pot’ conversion of aldehyde 6 to hydroxyketoester 10 with high enantioselection, culminating in a practical asymmetric synthesis of (3 R ,5 S ) isomer of the antihyperlipoproteinemic agent fluvastatin, 1 , is described. All four 3,5-dihydroxy-6( E )-heptenoate stereoisomers were prepared in enantiopure form starting from 10 , utilizing selective reduction and oxidation methods.

Selective deprotection of alkyl t-butyldimethylsilyl ethers in the presence of aryl t-butyldimethylsilyl ethers with bismuth bromide

Abstract Alkyl t -butyldimethylsilyl ethers can be selectively cleaved in the presence of aryl ethers using a catalytic amount of bismuth bromide in wet acetonitrile at ambient temperatures.