| Research Abstract |
The following results are obtained in this research project.
1. Creation and Reactions of Carbonyl Ylides and Related 1,3-Dipolar Reagents
1,3-Dipolar reagents are important and interesting chemical species from both synthetic and theoretical points of view. The novel findings that simple carbonyl ylides, otherwise inaccessible, were indeed expediently generated by the silicon-based 1,3-elimination from alpha-aryl-substituted chloromethyl trimethylsilylmethyl ether under mild and neutral conditions which provided the powerful one-step synthesis of dihydrofurans and tetrahydrofurans and related heterocylesvia [3+2] cycloadditions to a variety of multiple pi-bonds including C=C,C=C,C=O,C=S,C=N,N=N.
2. Unprecedented Samarium-Mediated Reactions : Generation of Non-Stabilized Carbonyl Ylids
Samarium reveals a strong reducing ability and by virue of this character together with its oxophilicity, is widely applied to organic synthesis in the formation of carbon-carbon bonds and transformation of
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a variety of functionalities with high selectivities. In the course of our study on the generation and reactions of reactive species, we report herein the generation of novel active species, nonstabilized carbonyl ylids from iodomethyl silyl ethers mediated by samarium, otherwise inaccessible, and their [3+2] cycloadditions to a variety of unsaturated compounds such as aldehydes, alkenes, allenes, and alkynes.
3. Direct Generation and Reactions of Sulfur-Substituted Allylcopper Reagents by a Novel Reduction Reaction Using Organocuprate
Ketene dithioacetals bearing a chlorine atom at an allylic position are cleanly reduced to generate the corresponding allylcopper reagents by treatment with two equimolar amounts of dimethylcuprate derived from cuprous cyanide (Me_2Cu (CN) Li_2). This reaction displays remarkable contrast to hitherto known reactions of cuprates in a sense of highly chemoselective reduction (only metal-halogen exchange reaction occurs) toward substitution reactions and is formally a new type of reaction for the generation of allylcopper species.
4. Silicon-Directed Cyclization of Vinylsilanes Bearing Hydroxy Group Catalyzed by an Acid
The acid-catalyzed cyclization of vinylsilanes bearing a hydroxy group took place cleanly to give tetrahydrofurans and tetrahydropyans, and the addition of hydroxy group to vinylsilane proceeded in a syn stereoselective fashion. Less
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