327620-61-1Relevant articles and documents
Asymmetric Kulinkovich Hydroxycyclopropanation of Alkenes Mediated by Titanium(IV) TADDOLate Complexes
Iskryk, Marharyta,Barysevich, Maryia,O?eka, Maksim,Adamson, Jasper,Kananovich, Dzmitry
supporting information, p. 1935 - 1948 (2019/04/26)
Asymmetric Kulinkovich cyclopropanation of carboxylic esters with prochiral alkenes is reported. The process is mediated by titanium(IV) (4 R,5 R)-TADDOLate complexes and affords correspondingly (Z)- or (E)-cyclopropanols with up to 84-87% ee in the event of intra- or intermolecular olefin ligand exchange in intermediate titanacyclopropane [titanium(II)-alkene] species. Configuration of the olefin double bond is preserved in the cyclopropane products, pointing out on total retention of configuration at Ti-C bond in the cyclopropane forming step. The results have been interpreted in the framework of ate complex mechanism, suggesting formation of pentacoordinated titanium ate species as a prerequisite of high enantiocontrol.
Deprotection of homoallyl (hAllyl) derivatives of phenols, alcohols, acids, and amines
Lipshutz, Bruce H.,Ghorai, Subir,Leong, Wendy Wen Yi
supporting information; experimental part, p. 2854 - 2857 (2009/08/08)
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Mechanistic Studies of the Biomimetic Epoxy Ester-Orthoester and Orthoester-Cyclic Ether Rearrangements
Giner, Jose-Luis,Li, Xiaoyong,Mullins, Joseph J.
, p. 10079 - 10086 (2007/10/03)
The relative rates of acid-catalyzed rearrangements of epoxy esters to [3.2.1]bicyclic orthoesters, the subsequent rearrangements of these ortho esters to substituted tetrahydrofurans, and the rates of orthoester hydrolysis at pH 4.75 were measured in NMR kinetics experiments. The ease of formation and stabilities of these orthoesters compared favorably with the OBO-type [2.2.2]bicyclic orthoesters typically used as protecting groups of carboxylic acids. Studies with 13C NMR-detected 18O-labeling show that epoxy ester rearrangement takes place preferentially via 6-exo cyclization, although the 7-endo process competes when the distal center of the epoxide is disubstituted. The ortho ester-cyclic ether rearrangement was shown by 18O-labeling to occur exclusively via intermediacy of a five-membered dioxonium ion. The structures of the hydrolysis products also indicate the intermediacy of a dioxolanium ion during hydrolysis. The implications for a hypothetical biosynthesis of marine polyether toxins are discussed.
