ABSTRACT
The development of highly enantio- and diastereoselective organocatalytic monofluorovinylations is presented. Based on the application of α-fluoro-ß-keto-benzothiazolesulfones, the formal addition of a monofluorovinylic anion synthon to a range of acyclic and cyclic enones, as well as imines, is shown. These procedures give selective access to both E- and Z-isomers of the monofluorovinylated products, which are isolated as the pure diastereoisomers in good to excellent yields with up to 99% ee. Furthermore, the application of this concept for the formation of highly enantioenriched bicylic compounds containing a monofluorovinyl moiety is also described. In addition, a mechanistic rationale for the observed E:Z-selectivities is presented.
Subject(s)
Fluorine/chemistry , Peptides/chemistry , Vinyl Compounds/chemistry , Catalysis , Molecular Structure , Stereoisomerism , Sulfones/chemistry , Thiazoles/chemistryABSTRACT
The mechanisms of the α-, ß- and γ-functionalisations of aldehydes and α,ß-unsaturated aldehydes by secondary amines are presented and discussed.
Subject(s)
Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Ketones/chemistry , Ketones/pharmacology , Organometallic Compounds/chemistry , Organometallic Compounds/chemical synthesis , Titanium/chemistry , Antineoplastic Agents/chemical synthesis , Cell Line, Tumor , Drug Screening Assays, Antitumor , Humans , Jurkat Cells , Ketones/chemical synthesis , Organometallic Compounds/pharmacology , Structure-Activity RelationshipABSTRACT
A method for the preparation of a variety of cyclobutanes via 4-exo cyclization of radicals is presented. Radical generation is carried out by electron transfer from titanocene(III) chlorides to epoxides. The reaction relies on the acceleration of the cyclization through the use of alpha,beta-unsaturated carbonyl compounds as radical traps and the thermodynamic stabilization of the cyclobutylcarbinyl radicals through conjugation. The mechanism of the transformation was investigated by a combined theoretical and experimental study. The computational results provide the crucial energetic and structural features of pertinent intermediates and transition structures. Moreover, the origins of the diastereoselectivity of the 4-exo cyclization are outlined for the first time. Catalysts for those cases where "Cp2TiCl" did not perform in a satisfactory manner have been devised. Through the introduction of tert-butyl or cyclo-hexyl substituted cyclopentadienyl ligands the longevity of the pivotal beta-titanoxy radicals is increased sufficiently enough to enable the slow but often surprisingly diastereoselective formation of the cyclobutylcarbinyl radical. The resulting transformation constitutes the first general approach to cyclobutanes using radical chemistry.
