75101-99-4Relevant articles and documents
Synthesis of highly functionalized [3]dendralenes and their Diels-Alder reactions displaying unexpected regioselectivity
Naidu, Gonna Somu,Singh, Rekha,Kumar, Mukesh,Ghosh, Sunil K.
, p. 37136 - 37148 (2016)
Acyclic tetrasubstituted [3]dendralenes stable towards D-A cyclodimerization were prepared by the double olefination of substituted dienyl phosphonates with dimethylsulfonium methylide, followed by H-W-E olefination of the formed butadienylphosphonoacetates with aldehydes. The X-ray structure of a [3]dendralene with a 4-position benzyl substitution revealed that an electron-rich diene exists in the s-trans conformation, leading to the stability. This structural preference of dendralenes leads to an unusual regioselectivity in the D-A reaction, wherein a deactivated diene participated in the process and displayed endo selectivity. The steric bulk of the groups at the 2 and 4 positions govern the regioselectivity and dominates the electronic effects. For the dendralenes possessing a 4-methyl substituent, the electronically rich diene participated in the D-A reaction. These D-A adducts failed to undergo further cycloaddition owing to steric crowding, which resulted in gauche conformation of the diene, as evidenced by X-ray structures of the adducts.
Asymmetric Nazarov Cyclizations of Unactivated Dienones by Hydrogen-Bond-Donor/Lewis Acid Co–Catalyzed, Enantioselective Proton-Transfer
Metternich, Jan B.,Reiterer, Martin,Jacobsen, Eric N.
, p. 4092 - 4097 (2020/09/01)
We report an enantioselective Nazarov cyclization catalyzed by chiral hydrogen-bond-donors in concert with silyl Lewis acids. The developed transformation provides access to tri-substituted cyclopentenones in high levels of enantioselectivity (up to 95% e.e.) from a variety of simple unactivated dienones. Kinetic and mechanistic studies are consistent with a reversible 4π-electrocyclization C?C bond-forming step followed by rate- and enantio-determining proton-transfer as the mode of catalysis. (Figure presented.).
Enantioselective Nazarov Cyclizations Catalyzed by an Axial Chiral C6F5-Substituted Boron Lewis Acid
Süsse, Lars,Vogler, Maria,Mewald, Marius,Kemper, Benedict,Irran, Elisabeth,Oestreich, Martin
supporting information, p. 11441 - 11444 (2018/08/28)
A chiral variant of B(C6F5)3 with a 3,3′-disubstituted binaphthyl backbone is shown to catalyze Nazarov cyclizations with high levels of enantio- and diastereocontrol. The parent B(C6F5)3 a
