Tuyen Nguyen Van

Synthesis of coumarins by ring-closing metathesis using Grubbs’ catalyst

A novel generally applicable synthesis of coumarins from phenolic substrates utilizing ring-closing metathesis is described. This sequence involves O-allylation of phenols followed by ortho-Claisen rearrangement, subsequent based-induced isomerization affording 2-(1-propenyl)phenols, acylation with acryloyl chloride, and finally ring-closing metathesis (RCM) with Grubbs’ second generation catalyst.

Synthesis of 6H-naphtho[2,3-c]chromene-7,12-diones via palladium-catalyzed intramolecular cyclization of 2-bromo-3-aryloxymethyl-1,4-naphthoquinones

Abstract 6H-Naphtho[2,3-c]chromene-7,12-diones, to be considered as tetracyclic derivatives of the natural product pentalongin, were conveniently synthesized for the first time via palladium-catalyzed intramolecular cyclization of 2-bromo-3-aryloxymethyl-1,4-naphthoquinones.

Synthesis of 1,3-disubstituted naphtho[2,3-c]pyran-5,10-diones

Abstract Two convenient and simple methods for the synthesis of 1,3-disubstituted naphtho[2,3- c ]pyran-5,10-diones, which involve the introduction of acylmethyl groups onto 2-(1-hydroxyethyl)-1,4-naphthoquinones and subsequent base- and acid-induced ring closure, were developed.

Synthesis of 3-alkyl- and 3-aryl-2-aza-anthraquinones

Abstract Reaction of 2-acylated 3-phenoxymethyl-1,4-naphthoquinones with aqueous ammonium hydroxide, provides a facile entry to 3-alkyl- and 3-aryl-benz[g]isoquinoline-5,10-diones.

New pentacyclic cyclol-type naphthohydroquinone from the roots of Pentas bussei

The novel naphthohydroquinone, methyl 5,10-dihydroxy-7-methoxy-1,1,3a-trimethyl-1a,2,3,3a,10c,10d-hexahydro-1H-4-oxacyclobuta[cd]indeno[5,6-a]naphthalene-9-carboxylate 2, was isolated from the hexane extract of dried roots of Pentas bussei. Its structure elucidation was done by detailed spectroscopic methods. It is the first cyclol moiety containing naphthohydroquinone to be reported, and a novel natural product from P. bussei.

New synthesis of the alkaloid polonicumtoxin C.

Abstract Two new short syntheses of the alkaloid polonicumtoxin C ( 3 ) are presented. In the first pathway, polonicumtoxin C was obtained in two steps by alkylation of 6-methyl-2,3,4,5-tetrahydropyridine with E -4-bromo-3-methyl-1-(tetrahydro-2-pyranyloxy)-2-butene 7 and subsequent deprotection of the THP group. In the second pathway, the cyclic ketimine was constructed via a short sequence of reactions involving (a) sequential alkylation of the N -(isopropylidene)isopropylamine with N , N -disilylprotected ω-bromopropylamine and E -4-bromo-3-methyl-1-(tetrahydro-2-pyranyloxy)-2-butene 7 , (b) transimination and deprotection, the latter two reactions occurring in one step.

Synthesis of Chiral cis-1,2,3-Trisubstituted Aziridines

Abstract Chiral cis-1,2,3-trisubstituted aziridines were conveniently synthesized from (1R,2S)-(−)- or (1S,2R)-(+)-norephedrine via the corresponding chiral N-(arylidene)-β-chloroamines. The enantiomeric purity of the chiral aziridines (e.e. >98%) was established by NMR spectroscopy utilizing (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol.

A NEW SYNTHESIS OF ALKYL 1-ALKYL-2-METHYLPYRROLE-3-CARBOXYLATES BY RING TRANSFORMATION OF 2-CHLORO-2-ACETIMIDOYLBUTYROLACTONES

Abstract Reaction of 2-chloro-2-acetimidoylbutyrolactones with sodium methoxide or sodium ethoxide in the corresponding alcohol provides a facile one-step synthesis of methyl or ethyl 1-alkyl-2-methylpyrrole-3-carboxylates from readily available starting materials.