Hsien-Jen Wu

The Pentaoxa[5]peristylanes. A Novel Oxa-Cage System

Abstract The synthesis of pentaoxa[5]peristylanes, a novel oxa-cage system, has been accomplished via ozonolysis of 7- anti -2,3- bis-endo -triacylbicyclo[2.2.1]-5-heptenes and via a direct chemical transformation of the tetraacetal tetraoxa-cages 5a–c and 6a–c .

Iodine-induced cyclization reaction of endo-thioester substituted norbornenes followed by methylthio group rearrangement

Abstract Treatment of the endo -thioester group substituted norbornenes 3a-3d with iodine in aqueous tetrahydrofuran at 25 °C gave the novel methylthio group rearranged lactonization products 4a-4d in 80% yields; iodolactonization reaction of 9 was applied to the synthesis of novel diacetal trioxa-cage compound 13 .

Synthesis of Diacetal Trioxa-cage Compounds via Reaction of Bicyclo[2.2.1]heptenes and Bicyclo[2.2.2]octenes with Dimethyldioxirane

Abstract A new entry for the synthesis of diacetal trioxa-cage compounds via oxirane-induced sequential cyclization reaction of 2,3-bis- endo -diacylbicyclo[2.2.1]-5-heptenes and 2,3-bis- endo -diacylbicyclo[2.2.2]-5-octenes is reported. In the case of bicyclo[2.2.2]octenes, sequential cyclization reaction induced by iodine as electrophile failed. We have also demonstrated that dimethyldioxirane can selectively oxidize hemiacetals to give lactones with the secondary hydroxy group intact.

Ozonolysis of 2-endo-7-anti-diacylnorbornenes. A new entry for the synthesis of 2,4,6,13-tetraoxapentacyclo[5.5.1.03,11.05,9.08,12]tridecanes

Abstract A new route for the synthesis of the title compounds 4a, 4b, 10a , and 10b has been developed via ozonolysis of 2- endo -7- anti -diacylnorbornenes 3a, 3b, 9a , and 9b . The synthesis of the unsubstituted (parent) compound 4a of tetraacetal tetraoxa-cages has been accomplished for the first time by this new entry. Ozonolysis reactions of 3a, 3b , and 9a were also performed in CDCl 3 for understanding the final ozonide structures and the ozonation chemistry. Ozonolysis of 3a, 3b , and 9a in CH 2 Cl 2 at −78 °C followed by treatment with triethylamine provided an indirect support for the structures of the final ozonides 11a, 11b , and 14 .

A novel one-pot conversion of tetraacetal tetraoxa-cages to aza-cages mediated by iodotrimethylsilane in acetonitrile

Abstract Treatment of the tetraacetal tetraoxa-cages 1a-f with excess of iodotrimethylsilane in acetonitrile at 25 °C gave the novel tetraacetal trioxamonoaza-cages 2a-f in 75–80% yields respectively, a novel one-pot conversion of oxa-cages to aza-cages.

Synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo-[5.5.1.02,6.03,11.05,9]tridecanes

Abstract The synthesis of 4-oxo- and 4- anti -formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.0 2,6 .0 3,11 .0 5,9 ]tridecanes has been accomplished. Ozonolysis of compounds 10a,b and 12a-c in dichloromethane at −78 °C followed by reduction with dimethyl sulfide gave the title compounds, 4-oxo-tetraoxa-cages 11a,b and 14a-c , in moderate yields. Ozonolysis of the endo-syn isomers 15a,b and 18a,b under the same reaction conditions gave 4- anti -formyl-tetraoxa-cages 17a,b and 20a,b , respectively.

INTRAMOLECULAR DIELS-ALDER REACTION OF FURANS WITH ALLENYL ETHERS FOLLOWED BY METHYLTHIO GROUP 1,4-REARRANGEMENT

Abstract The base-catalyzed intramolecular Diels-Alder reactions of the furfuryl propargyl ethers 1a–1e gave compounds 6a–6e as the major product respectively, a novel reaction involving an intramolecular Diels-Alder reaction followed by a methylthio group 1,4-rearrangement.

Chemical transformation of tetraacetal tetraoxa-cages to aza-cages and amido-cages mediated by iodotrimethylsilane and the combination of chlorotrimethylsilane and sodium iodide in nitriles

Abstract An one-pot conversion of tetraacetal tetraoxa-cages 1a-e to aza-cages 2a-e mediated by iodotrimethylsilane in alkyl nitriles at 25 °C via the ring expansion compound 9 as the reaction intermediate was discovered. A Ritter-type reaction was proposed for the mechanism of this conversion. On the other hand, reaction of tetraacetal tetraoxa-cages 1 with Me 3 SiCl and NaI in nitriles at 25 °C gave the amido-cages 12 . Conjugated nitriles and Lewis acids, such as TiCl 4 or BF 3 ·OEt 2 were found to be ineffective for the conversion of oxa-cages to aza-cages. The structures of 2a and chemical transformation product 16 were proven by X-ray analysis.

INTRAMOLECULAR DIELS-ALDER REACTION OF FURANS WITH ALLENYL ETHERS FOLLOWED BY TRIMETHYLSILYL GROUP 1,2-REARRANGEMENT AND BROOK REARRANGEMENT

The base-catalyzed intramolecular Diels-Alder reactions of 5- trimethylsilyl-2 -furfuryl propargyl ethers la-lf gave compounds 2a-2f and 3a-3f in 70-90% yields respectively, a novel reaction involving an intramolecular Diels-Alder reaction followed by a trimethylsilyl group 1,2- rearrangement and Brook rearrangement. Copyright

A novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids

Treatment of tetraoxa-cages 1a–f with Lewis acids such as TiCl 4 , AlCl 3 , BF 3 ·OEt 2 and MeSO 3 H in dichloromethane at 25 °C gives the rearrangement products 2a–f in 90% yields regioselectively and stereoselectively; a novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids.