Browsing by Author "Chein, RJ"

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A synthesis of 6-myoporol
(1997-05-01)
Ho, TL
;
Chein, RJ
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
An approach to (+/-)-6-myoporol (1) featured stereocontrol by equilibration of 2,6-disubstituted cyclohexanones to mainly the cis isomer. The synthesis was completed by reaction of a lactone intermediate with 3-lithiofuran, Mitsunobu reaction, and hydrolysis.
A synthesis of 6-myoporol
(1997-05-01)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
An approach to (+/-)-6-myoporol (1) featured stereocontrol by equilibration of 2,6-disubstituted cyclohexanones to mainly the cis isomer. The synthesis was completed by reaction of a lactone intermediate with 3-lithiofuran, Mitsunobu reaction, and hydrolysis.
Intervention of phenonium ion in Ritter reactions
(2004-01-23)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
The transformation of phenylethyl chloride to 3,4-dihydroisoquinolines is shown to proceed via phenonium ion. The evidence comes from a study of dideuterated analogue 4, and the monomethylated and dimethylated compounds 2 and 3.
Ionization of 2-halo-1,1-difluoro-1-arylethanes in the presence of nitriles.
(2004-08-22)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
Ritter reaction of 1-aryl-1-fluoro-2-haloethanes
(2006-04-01)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
Fluorinated phenethyl bromides 1, 2, and 3, prove to be totally inert under Ritter reaction conditions in the presence of either SnCl4 or AgNO3, due to the strong deactivation by the gem-difluoro unit. Subjecting 2-bromo-1-fluoro-1-phenylethane to SnCl4 in MeCN at elevated temperatures led to formation of 2-methyl-4-phenyl-4,5-dihydrooxazole.
Synthesis of (-)-furodysinin from (+)-limonene
(1996-05-21)
Ho, TL
;
Chein, RJ
;
應用數學系
;
Department of Applied Mathematics
Furodysinin is synthesised by elaboration of (1R, 2R)-(+)-limonene oxide; key reactions include a tandem Claisen rearrangement-ene reaction and trapping of a conjugate adduct of an enone providing a bicyclic precursor of the sesquiterpene.
Synthesis of (-)-furodysinin from (+)-limonene
(1996-05-21)
Ho, TL
;
Chein, RJ
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
Furodysinin is synthesised by elaboration of (1R, 2R)-(+)-limonene oxide; key reactions include a tandem Claisen rearrangement-ene reaction and trapping of a conjugate adduct of an enone providing a bicyclic precursor of the sesquiterpene.
Total synthesis of (+)-beta-himachalene
(2006)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
An enantioselective synthesis of (+)-beta-himachalene (2) was accomplished starting from (1S,2R)-1,2-epoxy-p-menth-8-ene (3) in 15 or 16 steps with an overall yield of ca. 6% (Schemes 3, 5, and 6). Key transformations include an Ireland Claisen rearrangement, a Corey oxidative cyclization, and a ring expansion.
Total synthesis of (+/-)-2-isocyanoallopupukeanane
(2000-09-08)
Ho, TL
;
Kung, LR
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
2-Isocyanoallopupukeanane (4) has been obtained in racemic form from methyl 2-exo-methylbicyclo-[2.2.1]hept-5-ene-2-endo-carboxylate via dibromocarbene addition, S(N)2' displacement, chain extension, and elaboration of the unsaturated ketone 12c which underwent an intramolecular hetero-Diels-Alder reaction to afford 13 containing all the skeletal carbon atoms. The dihydropyran unit was cleaved by ozonolysis to give the tricarbocyclic intermediate which required seven more steps to complete the synthesis.
Unusual thionation via fragmentation
(2005-12-01)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
Reaction of 4,4-dichloro-2,6-diphenyl-4,4-dihydropyrane (2) with thiols in the presence of triethylamine gives interesting results. The exclusive formation of 2,6-diphenylpyran-4-thione (3) in the reaction with PhSH through cleavage of C-Ar-S bond is remarkable.