2006 Fiscal Year Final Research Report Summary
Organic Syntheses using Highly Reactive and Functional Organometallics
| Project/Area Number |
16350050
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Synthetic chemistry
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| Research Institution | University of Tsukuba |
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Principal Investigator |
HOSOMI Akira University of Tsukuba, Professor Emeritus, 名誉教授 (00004440)
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| Co-Investigator(Kenkyū-buntansha) |
HOJO Makoto University of Tsukuba, Graduate School of Pure and Applied Sciences, Associate Professor, 大学院数理物質科学研究科, 助教授 (50229150)
MIURA Katsukiyo University of Tsukuba, Graduate School of Pure and Applied Sciences, Associate Professor, 大学院数理物質科学研究科, 助教授 (20251035)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Vinylsilanes / Catalytic Process / Organic Syntheses / Mixed Lewis acid / Active Species / Organosilicon Chemistry / Organometallic Chemistry / Manganate Reagents |
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| Research Abstract |
1. Preparation of Dimethylsilyl-Protected Nucleophiles and Their Use for Organic Synthesis :
Most of organosilicon reagents have a trimethylsilyl (TMS) group or a more bulky triorganosilyl group. Synthetic utility of silicon reagents bearing a less bulky silyl group has remained unexplored. We have found that dimethylsilyl (DMS)-protected nucleophiles are more reactive than TMS-protected nucleophiles. For example, in the presence of CaCl_2, ketone DMS enolates added smoothly to aldehydes at 30 ℃ in DMF to give aldols in high yield. In the reaction of DMS enolates, CaCl_2 would serve as Lewis base to activate the enolates by nucleophilic attack of the silicon by the chloride ion. DMS enolates are useful for the Mannich-type reaction of N-tosylimines and the Michael reaction of α-enones. Similarly, α-DMS-esters are more reactive than the corresponding TMS-based reagents. In the presence of metal chlorides (LiCl, MgCl_2, etc.), aldehydes and ketones underwent efficient aldol reactions of a
… More
-DMS-esters.
We have developed the tandem aldol-reduction reaction of aldehydes with DMS enolates, which directly forms 1,3-diols stereoselectively. In this case, DMS enolates play two roles of carbon nucleophile and reductant. We have also demonstrated that DMS ethers and amines are valuable for reductive etherification and amination of carbonyls in the presence of a Lewis acid.
2. Reduction and Carbon-Carbon Bond Formation under Catalysis by Indium Salts :
We have found that PhSiH_3 reacts with haloalkanes in the presence of In(OAc)_3 to form the dehalogenated alkanes. This reduction would involve a radical chain mediated by indium hydride species. The PhSiH_3-In(OAc)_3 system is applicable to intermolecular radical addition of haloalkanes to electron-deficient alkenes. Additionally, it is valuable also for reductive aldol reaction of a-enones with aldehydes.
We have succeeded in indium salt-promoted intramolecular addition of allylstannanes, allylsilanes, and silyl enolates to unactivated alkynes. The addition of allylstannanes proceeds probably by Sn-In transmetalation and subsequent allylindation, while the addition of allylsilanes and silyl enolates would involve electrophilic activation of the triple bond with the indium salts followed by nucleophilic addition of these silyl-protected nucleophiles. In the reaction of silyl enolates, the resultant vinylindium species can be used for further reaction with heteroatom and carbon electrophiles. Less
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