111171-94-9Relevant articles and documents
Lewis Acid Catalyzed Cyclizations of Epoxidized Baylis-Hillman Products: A Straightforward Synthesis of Octahydrobenzo[e]azulenes
Konopacki, Donald B.,Shortsleeves, Kelley C.,Turnbull, Mark M.,Wikaira, Jan L.,Hobson, Adrian D.
, p. 5453 - 5463 (2015)
Tricyclic keto-diols have been synthesized from 2-cyclopenten-1-one in a three-step annulation procedure. The importance of aryl ring electronics and steric contributions and the choice of Lewis acid were investigated for the final cyclization step. An unexpected cyclization product was identified, suggesting multiple mechanisms for the cyclization process. The Lewis acid catalyzed Baylis-Hillman reaction has been used for the stereoselective synthesis of fused 5-7-6 ring systems. The isolation of an unexpected regioisomer from the reaction with (methylphenyl)propionaldehyde provides insights into the probable mechanisms operative in the reaction.
Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
supporting information, p. 4867 - 4875 (2021/09/14)
The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
A Case Study in Catalyst Generality: Simultaneous, Highly-Enantioselective Br?nsted- And Lewis-Acid Mechanisms in Hydrogen-Bond-Donor Catalyzed Oxetane Openings
Strassfeld, Daniel A.,Algera, Russell F.,Wickens, Zachary K.,Jacobsen, Eric N.
supporting information, p. 9585 - 9594 (2021/07/19)
Generality in asymmetric catalysis can be manifested in dramatic and valuable ways, such as high enantioselectivity across a wide assortment of substrates in a given reaction (broad substrate scope) or as applicability of a given chiral framework across a variety of mechanistically distinct reactions (privileged catalysts). Reactions and catalysts that display such generality hold special utility, because they can be applied broadly and sometimes even predictably in new applications. Despite the great value of such systems, the factors that underlie generality are not well understood. Here, we report a detailed investigation of an asymmetric hydrogen-bond-donor catalyzed oxetane opening with TMSBr that is shown to possess unexpected mechanistic generality. Careful analysis of the role of adventitious protic impurities revealed the participation of competing pathways involving addition of either TMSBr or HBr in the enantiodetermining, ring-opening event. The optimal catalyst induces high enantioselectivity in both pathways, thereby achieving precise stereocontrol in fundamentally different mechanisms under the same conditions and with the same chiral framework. The basis for that generality is analyzed using a combination of experimental and computational methods, which indicate that proximally localized catalyst components cooperatively stabilize and precisely orient dipolar enantiodetermining transition states in both pathways. Generality across different mechanisms is rarely considered in catalyst discovery efforts, but we suggest that it may play a role in the identification of so-called privileged catalysts.
Iridium Complex-Catalyzed C2-Extension of Primary Alcohols with Ethanol via a Hydrogen Autotransfer Reaction
Kobayashi, Masaki,Itoh, Satoshi,Yoshimura, Keisuke,Tsukamoto, Yuya,Obora, Yasushi
, p. 11952 - 11958 (2020/10/23)
The development of a C2-extension of primary alcohols with ethanol as the C2 source and catalysis by [Cp*IrCl2]2 (where Cp? = pentamethylcyclopentadiene) is described. This new extension system was used for a range of benzylic alcohol substrates and for aliphatic alcohols with ethanol as an alkyl reagent to generate the corresponding C2-extended linear alcohols. Mechanistic studies of the reaction by means of intermediates and deuterium labeling experiments suggest the reaction is based on hydrogen autotransfer.
