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Highly Efficient and Convenient Acid Catalyzed Hypersilyl Protection of Alcohols and Thiols by Tris(trimethylsilyl)silyl-N,N-dimethylmethaneamide
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, A-8010 Graz, Austria.
Vise andre og tillknytning
2012 (engelsk)Artikkel i tidsskrift (Annet vitenskapelig) Submitted
Abstract [en]

Tris(trimethylsilyl)silyl-N,N-dimethylmethaneamide, herein named hypersilylamide, is a convenient and efficient source of the hypersilyl group in the first widely applicable acid catalyzed protocol for silyl group protection of primary, secondary, tertiary alkyl as well as aryl alcohols and thiols in high yields. The sole by-product is N,N-dimethylformamide (DMF) and a range of solvents can be used, including DMF. A high selectivity in the protection of diols can be achieved, also for diols with very small differences in the steric demands at the two hydroxyl groups. Moreover, in the protection of equivalent alcohol and thiol sites the protection of the alcohol is faster, allowing for selective protection in high yields. Quantum chemical calculations at the M062X hybrid meta density functional theory level give insights on the mechanism for the catalytic process. Finally, the hypersilyl group is easily removed from all protected alcohols and thiols examined herein by irradiation at 254 nm.

sted, utgiver, år, opplag, sider
2012.
HSV kategori
Forskningsprogram
Kemi med inriktning mot oorganisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-169781OAI: oai:DiVA.org:uu-169781DiVA, id: diva2:507686
Tilgjengelig fra: 2012-03-06 Laget: 2012-03-06 Sist oppdatert: 2013-03-07bibliografisk kontrollert
Inngår i avhandling
1. Low-coordinate Organosilicon Chemistry: Fundamentals, Excursions Outside the Field, and Potential Applications
Åpne denne publikasjonen i ny fane eller vindu >>Low-coordinate Organosilicon Chemistry: Fundamentals, Excursions Outside the Field, and Potential Applications
2012 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis reports on unsaturated silicon compounds, as well as excursions from these into germanium chemistry, single molecule electronics, and silyl protective group chemistry. Both experimental and computational investigations were performed.

Potassium germenolates were synthesized through reactions of tris(timethylsilyl) substituted acyl- and carbamylgermanes with potassium tert-butoxide. The potassium germenolates calculated by density functional theory have pyramidal structures at the Ge atoms, similar to the Si in the corresponding potassium silenolates, indicating negative charge on germanium rather than on oxygen. Germenolates also display germyl anion-like reactivity instead of germene-like reactivity as they are alkylated at Ge and initiate anionic polymerization of dienes rather than form [4+2] cycloadducts. The NMR chemical shifts reveal more negative charge at Ge in germenolates than at Si in analogous silenolates.

Computations indicate that silabenzenes and silapyridines are reachable via [1,3]-silyl shifts from cyclic conjugated acylsilanes. Differently sized substituents were considered to prevent dimerizations, and 1-triisopropylsilyl-2-triisopropylsiloxy-6-tert-butylsilabenzene is a good synthetic target. Computations also show that silaphenolates are species with negative charge primarily localized at oxygen atom. Their planar structures, bond lengths, and NICS values reveal significant influence of aromaticity. Electrostatic repulsion should increase their stability, however, steric bulk is also important.

Furthermore, it was found computationally that [1,3]-silyl shift from an acylsilane to a silene can function as a molecular switch reaction. Conductance calculations support this proposition.  

Finally, tris(trimethylsilyl)silylmethaneamide (hypersilylamide) together with catalytic amounts of triflic acid were found to be efficient for protection of a range of alkyl and aryl alcohols and thiols in good to excellent yields. The protocol can be used to protect the less hindered OH group of a diol and has a broad functional group tolerance. A catalytic cycle is proposed. Hypersilyl protected alcohols and thiols are deprotected efficiently under photolytic conditions.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2012. s. 75
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 907
Emneord
organosilicon, silene, silaaromatics, silenolate, hypersilyl group, alcohol protection, molecular switch
HSV kategori
Forskningsprogram
Kemi med inriktning mot organisk kemi
Identifikatorer
urn:nbn:se:uu:diva-169796 (URN)978-91-554-8296-1 (ISBN)
Disputas
2012-04-21, B7:101a, BMC, Husargatan 3, Uppsala, 13:30 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2012-03-30 Laget: 2012-03-06 Sist oppdatert: 2012-04-19bibliografisk kontrollert

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