Precatalyst‐Enabled Selectivity: Enantioselective NiH‐Catalyzed
anti
‐Hydrometalative Cyclization of Alkynones to
Endo
‐ and Heterocyclic Allylic Alcohols
摘要:
AbstractA highly enantioselective NiH‐catalyzed hydrocyclization of alkynones with unparalleled anti‐ and endocyclic selectivities is described. The choice of the precatalysts has significant influence in tuning the regio‐ and enantioselectivity. Using Ni(OTs)2/Phox as a precatalyst and (EtO)2MeSiH as a hydride source, an array of enantioenriched O‐, N‐, and S‐containing heterocyclic tertiary allylic alcohols are obtained in 24–81 % yields with 80:20–99:1 er. Mechanistic investigations and synthetic application are also carried out. This study represents an efficient access to a set of allylic alcohols that are unable to access by the state‐of‐the‐art coupling reactions.
The first asymmetric nickel‐catalyzed intramolecular reductivecyclization of alkynones is reported. A P‐chiral monophosphine and triethylsilane were used as the ligand and the reducing reagent, respectively, to form a series of tertiary allylic alcohols bearing furan/pyran rings in excellent yields and enantioselectivities. This reaction has a broad substrate scope and enabled the efficient synthesis
The photochemically initiated dehydro-Diels-Alder (PDDA) reaction is an efficient and versatile method for the prepa- ration of biaryls. The ring closure may take place both inter- and in- tramolecularly, of which the intramolecular variant is more productive from the preparative point of view. A variety of linkers can be employed to connect the ynone moiety, which acts as the chromophore, with another