- Zirconocene-catalyzed direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio under solvent-free conditions
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A highly efficient way for the direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio using a zirconocene complex (1, 1 mol%), a strong Lewis acid of good water tolerance, as a catalyst under solvent-free conditions has been developed. A wide range of acid and alcohol (esters) substrates undergo (trans)esterification to produce carboxylic ester motifs in moderate to good or excellent yields with good functional tolerance, such as that towards C-Br as well as CC and CC bonds. And complex 1 can be recycled six times without showing a significant decline in catalytic efficiency. It was demonstrated that cyclandelate, which is used to treat high blood pressure as well as heart and blood-vessel diseases, can be directly synthesized on a gram scale with 81% yield (6.70 g) using complex 1.
- Tang, Zhi,Jiang, Qiutao,Peng, Lifen,Xu, Xinhua,Li, Jie,Qiu, Renhua,Au, Chak-Tong
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supporting information
p. 5396 - 5402
(2017/11/22)
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- Nucleophilic iron catalysis in transesterifications: Scope and limitations
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Figure presented The ester bond is one of the most common structural motifs found in nature. Apart from the condensation between an acid and an alcohol, transesterifications represent another mechanistic alternative for the preparation of this compound class. The present paper summarizes our most recent investigations in this field, using nucleophilic iron complexes as catalysts for transesterifications under neutral conditions. This new type of metal catalyst complements the existing methodologies, which rely on Lewis acidic metal complexes. Investigations on scope and limitations, stereochemical course, and chemoselectivities will be presented.
- Magens, Silja,Plietker, Bernd
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supporting information; experimental part
p. 3715 - 3721
(2010/08/07)
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- Fragrance precursor compounds
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Organosiloxane fragrance precursor compounds having at least one organosiloxane unit of the formula or a mixture thereof and if any other siloxane unit(s) in the said organosiloxanes being present this/these is/are of formula wherein R represents a substituted or unsubstituted C1-8alkyl group or a substituted or unsubstituted aryl group; R″ represents a hydrogen atom, a monovalent C1-8hydrocarbon group or a monovalent C1-8halogenated hydrocarbon group; R1represents a hydrogen atom or a substituted or unsubstituted C1-8alkyl group or a substituted or unsubstituted aryl group or a bond connecting CR1and CR3; R3represents a hydrogen atom or a substituted or unsubstituted C1-8alkyl group or a substituted or unsubstituted aryl group; represents (CR42)nwhereby R4represents a substituted or unsubstituted C1-8alkyl group or a substituted or unsubstituted aryl group or a hydrogen atom and whereby n is from 0-20 and each R4is the same or different; OR2represents the residue of an olfactive alcohol or of the enol form of an olfactive aldehyde or olfactive ketone; is 0, 1 or 2; and is 0, 1, 2 or 3. The compounds can be used in the manufacture of odorant compositions used in the preparation of cosmetic and laundry products.
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