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Radical cyclizations of acylsilanes in the synthesis of (+)-swainsonine and formal synthesis of (−)-epiquinamide. Tetrahedron 2011. [DOI: 10.1016/j.tet.2010.12.048] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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2
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Chang CC, Kuo YH, Tsai YM. The synthesis of carbohydrate-derived acylsilanes and their intramolecular free radical cyclizations with the formation of polyoxygenated cyclopentanes. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.04.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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3
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Ueng SH, Chen MJ, Chu SF, Shao YF, Fan GT, Chang SY, Tsai YM. The Scope and Limitations of 1,3-Stannyl Shift-Promoted Intramolecular Cyclizations of α-Stannyl Radicals with a Formyl Group. J Org Chem 2006; 71:1502-12. [PMID: 16468799 DOI: 10.1021/jo052176v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Alpha-tributylstannyl radicals can be generated from the corresponding bromides or xanthates. These radicals undergo efficient intramolecular 1,5-cyclizations with a formyl group. The resulting beta-stannyl alkoxy radicals proceed through a 1,3-stannyl shift from carbon to oxygen to afford beta-stannyloxy radicals. This novel rearrangement is most likely irreversible and serves as a driving force to promote the cyclizations. Although the cyclization rates can be accelerated when the formyl group carries alpha-dimethyl substituents, unfortunately beta-scission of the alkoxy radicals becomes competitive with the 1,3-stannyl shift. The beta-stannyloxy radicals can be employed in further cyclizations to obtain tandem cyclization products.
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Affiliation(s)
- Shau-Hua Ueng
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
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Marion F, Calvet S, Marié JC, Courillon C, Malacria M. Silylated Vinyloxiranes – Recent Advances and Synthetic Applications. European J Org Chem 2006. [DOI: 10.1002/ejoc.200500578] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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5
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Marié JC, Courillon C, Malacria M. SN2′ Reactions between Lithiated Carbon Nucleophiles and Silylated Vinyloxiranes – Effects of Salts and Solvents on the Stereocontrol. European J Org Chem 2006. [DOI: 10.1002/ejoc.200500666] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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6
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Yu Y, Feng S, Feng D. An ab Initio Study on Thermal Rearrangement Reactions of 1-Silylprop-2-en-1-ol H3SiCH(OH)CHCH2. J Phys Chem A 2005; 109:3663-8. [PMID: 16839032 DOI: 10.1021/jp045892u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2 were studied by ab initio calculations at the G2(MP2) and G3 levels. The reaction mechanisms were revealed through ab initio molecular orbital theory. On the basis of the MP2(full)/6-31G(d) optimized geometries, harmonic vibrational frequencies of various stationary points were calculated. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations. The results show that the thermal rearrangements of H3SiCH(OH)CH=CH2 happen in two ways. One is via the Brook rearrangement reactions (reaction A), and the silyl group migrates from carbon atom to oxygen atom passing through a double three-membered ring transition state, forming allyloxysilane CH2=CHCH2OSiH3. In the other, the reactant undergoes a dyotropic rearrangement; the hydroxyl group migrates from carbon atom to silicon atom coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, forming allylsilanol CH2=CHCH2SiH2OH (reaction B). The barriers for reactions A and B were computed to be 343.5 and 203.7 kJ/mol, respectively, at the G3 level. The changes of the thermodynamic functions, entropy (DeltaS), entropy (DeltaS(doubledagger)) for the transition state, enthalpy (DeltaH), and free energy (DeltaG) were calculated by using the MP2(full)/6-31G(d) optimized geometries, and harmonic vibrational frequencies of reactants, transition states, and products with statistical mechanical methods, and equilibrium constant K(T) and reaction rate constant k(T) in canonical variational transition-state theory (CVT) with centrifugal-dominant small-curvature tunneling approximation (SCT) were calculated over a temperature range 400-1300 K. The conventional transition-state theory (TST) rate constants were also calculated for the purposes of comparison. The influences of the vinyl group attached to the center carbon of the alpha-silyl alcohols on reactions were discussed.
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Affiliation(s)
- Yongming Yu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China
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The study of intramolecular tandem radical cyclizations of acylsilanes with radicalphiles attached on silicon. Tetrahedron 2005. [DOI: 10.1016/j.tet.2004.12.053] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Yu Y, Feng S. An ab Initio Study on [1,2] Rearrangement Reactions of Silylmethanol H3SiCH2OH. J Phys Chem A 2004. [DOI: 10.1021/jp048197v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yongming Yu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China, and School of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P.R. China
| | - Shengyu Feng
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China, and School of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P.R. China
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Stereoselective lithiation of α,β-epoxy-γ,δ-vinylsilanes and transformation into α-silylated ketones. Tetrahedron 2003. [DOI: 10.1016/j.tet.2003.10.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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10
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Huang CH, Chang SY, Wang NS, Tsai YM. The application of intramolecular radical cyclizations of acylsilanes in the regiospecific formation of cyclic silyl enol ethers. J Org Chem 2001; 66:8983-91. [PMID: 11749631 DOI: 10.1021/jo010883s] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acylsilanes with terminal alpha-stannyl bromide or xanthate functionalities are prepared. Alpha-stannyl radicals generated from these acylsilanes undergo intramolecular cyclizations to give cyclic silyl enol ethers regiospecifically. The radical processes involve radical cyclization, Brook rearrangement, and beta-fragmentation in sequence. A tributylstannyl group serves as the radical leaving group. The newly formed sigma-bond and pi-bond are located between the same two carbon atoms. This approach is limited to the formation of five-membered rings. In another route, omega-bromo-alpha-phenylsulfonylacylsilanes are synthesized. The radical cyclizations of these alpha-sulfonylacylsilanes also give cyclic silyl enol ethers. The phenylsulfonyl moiety is the radical leaving group in this system. Furthermore, the newly formed sigma-bond and pi-bond are located at adjacent positions sharing a single carbon atom. The latter approach is effective for both five- and six-membered ring formation.
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Affiliation(s)
- C H Huang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
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12
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On the radical brook rearrangement. Reactivity of alpha-silyl alcohols, alpha-silyl alcohol nitrite esters, and beta-haloacylsilanes under radical-forming conditions. J Org Chem 2000; 65:2292-304. [PMID: 10789438 DOI: 10.1021/jo9912855] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two alkoxyl radical generation methods, lead tetraacetate treatment of alcohols and photolysis of nitrites, were applied to alpha-silyl alcohols 21 and to the corresponding nitrites 25 with a view to forming alpha-silyl alkoxyl radicals 23 and studying their possible radical Brook rearrangement to alpha-silyloxy carbon radicals 24. LTA treatment of 21 led to their quick and efficient conversion into mixed acetyl-silyl acetals 33 under very mild conditions. Photolysis of alpha-alkylmonosubstituted alpha-silyl nitrites 25 to the corresponding aldehydes is considered to proceed through alpha-silyl alkoxyl radical intermediates 23. A concerted process is, however, proposed for the case of the benzyl nitrites analogues. On the basis of these results, it is postulated that resonance stabilization can have a major influence on the evolution of alpha-silyl alkoxyl radicals: should this stabilization be possible, they quickly evolve by alpha-silyl fragmentation; otherwise, they tend to undergo radical Brook rearrangement. It was also found that the radical Brook rearrangement of alpha-silyl cyclopropyloxyl radicals generated from beta-bromoacylsilanes under standard tin-radical conditions is too slow to compete with beta-fragmentation.
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Jiaang WT, Lin HC, Tang KH, Chang LB, Tsai YM. The Study of the Kinetics of Intramolecular Radical Cyclizations of Acylsilanes via the Intramolecular Competition Method. J Org Chem 1999. [DOI: 10.1021/jo982079k] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Weir-Torn Jiaang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Hsien-Chang Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Kuo-Hsiang Tang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Lih-Bin Chang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Yeun-Min Tsai
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
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Chang SY, Jiaang WT, Cherng CD, Tang KH, Huang CH, Tsai YM. The Scope and Limitations of Intramolecular Radical Cyclizations of Acylsilanes with Alkyl, Aryl, and Vinyl Radicals. J Org Chem 1997. [DOI: 10.1021/jo9711302] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sheng-Yueh Chang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Weir-Torn Jiaang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Chaur-Donp Cherng
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Kuo-Hsiang Tang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Chih-Hao Huang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
| | - Yeun-Min Tsai
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
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Tsai YM, Tang KH, Jiaang WT. Group transfer from silicon to carbon via tandem radical cyclizations of acylsilanes. Tetrahedron Lett 1996. [DOI: 10.1016/0040-4039(96)01773-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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17
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Le Bideau F, Gilloir F, Nilsson Y, Aubert C, Malacria M. Stereocontrolled synthesis of α-trialkylsilyl-β, γ-unsaturated aldehydes via palladium (0) catalysis. Synthetic usefulness. Tetrahedron 1996. [DOI: 10.1016/0040-4020(96)00264-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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18
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Chuang TH, Fang JM, Jiaang WT, Tsai YM. Reductions, Reductive Alkylations, and Intramolecular Cyclizations of Acyl Silanes with Samarium Diiodide or Tributyltin Hydride. J Org Chem 1996; 61:1794-1805. [PMID: 11667051 DOI: 10.1021/jo951980m] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of acyl silanes including aliphatic-, aromatic-, and bis-acyl silanes, as well as the acyl silanes bearing other substituents such as a bromine atom and alkenyl, succinimide, and carbonyl groups, were prepared, and their reactions with samarium diiodide or tributylstannane were studied. The reactions of acyl silanes occurred in various manners such as reductions, reductive alkylations, intramolecular radical cyclizations, pinacol couplings, aldol reactions, and Tishchenko reactions, depending on the nature of substrates and reaction conditions. Acyl silanes were generally reduced to give the corresponding alpha-silyl alcohols without transfer of silyl groups. Intramolecular radical cyclizations of 5-hexenoyl silanes and 1-silyl-1,5-pentanedione were realized to give alpha-silyl cyclopentanols and 1,2-cyclopentanediol derivatives, respectively. On treatment with samarium diiodide in tetrahydrofuran, 1-(trimethylsilyl)-1,6-hexanedione underwent a pinacol coupling reaction in the presence of t-BuOH, whereas it underwent a Tishchenko reaction in the presence of MeOH. The Tishchenko reaction of 1-silyl-1,5-pentanedione gave a delta-silyl-delta-lactone. On treating with samarium diiodide, 1-(trimethylsilyl)-1,5-hexanedione and 1,5-bis(trimethylsilyl)-1,6-hexanedione, underwent, respectively, intramolecular aldol reactions.
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Affiliation(s)
- Tsung-Hsun Chuang
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, Republic of China
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Bideau FL, Gilloir F, Nilsson Y, Aubert C, Malacria M. Stereoselective addition of nucleophiles on α-trialkylsilyl-β,γ-unsaturated aldehydes. Tetrahedron Lett 1995. [DOI: 10.1016/0040-4039(95)00084-p] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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