Here we report a new type of chiral all-carbon tetrasubstituted VQMs generated via chiral phosphoric acids catalyzed nucleophilic addition of 2-alkynylnaphthols to o-quinone methides or imines, which can be captured intramolecularly as a result of cycloaddition reaction. A new class of naphthyl-2H-chromenes bearing axially and centrally chiral elements and axially chiral quinone-naphthols were prepared efficiently with good to excellent yields, diastereoselectivities and enantioselectivities. Noteworthy, the enantioselective cycloaddition of alkynylnaphthols with o-quinone methides proceeded via a [2+2] cycloaddition, followed by a retro-4π-electrocyclization and a 6π re-cyclization. While the cycloaddition of alkynylnaphthols with imines proceeded via a sequential [2+4] cycloaddition and an auto oxidation reaction. Moreover, the obtained axially chiral naphthols can be converted into valuable phosphine ligands and other functional molecules.
The first highly enantioselective [3 + 2] formal cycloaddition of 1-styrylnaphthols (or phenol) with quinones catalyzed by a chiral phosphoric acid has been reported. A class of trans-2,3-diarylbenzofurans were prepared efficiently (up to 99% yield, >20:1 dr, 99% ee). This organocatalytic procedure allows lowering of the catalyst loading to 0.5 mol % without considerable loss in reactivity and enantioselectivity.
Asymmetric Prins cyclization of in
situ generated quinone methides and o-aminobenzaldehyde
has been developed with chiral phosphoric acid as an efficient catalyst.
This unconventional method provides a facile access to diverse functionalized
trans-fused pyrano-/furo-tetrahydroquinoline derivatives in excellent
yield and with excellent diastereo- and enantioselectivities (up to
99% yield and 99% ee). Mechanistic studies suggested that the three
adjacent tertiary stereocenters were constructed through the sequential
formation of C–O, C–C, and C–N bonds.
An enantioselective sulfenylation of β-naphthols has been developed for the first time using a newly synthesized cinchona-derived thiourea as the catalyst and N-(arylthio) succinimide (or phthalimide) as an electrophilic sulfur source. Various enantioenriched naphthalenones with an S-containing all-substituted stereocenter were prepared via a dearomatization strategy under mild reaction conditions.
An enantioselective arylative dearomatization reaction of β-naphthols with quinone monoimides has been developed for the first time using a chiral phosphoric acid as the catalyst, the desired enantioenriched cyclohexadienones were prepared with excellent yields and enantioselectivities by a domino Michael addition and aromatization process (up to 99 % yield, up to 98 % ee). This process is operationally simple and readily scaled up, as well as a broad substrate scope which includes 1-substituted-2-naphthols with/without 3-substituents. Furthermore, this organocatalytic procedure allows the lowering of catalyst loading to 0.5 mol % without considerable loss in reactivity and enantioselectivity.
We describe a Pd-catalyzed selective
C–H arylation reaction
of phenylacetaldehydes using l-valine as the transient directing
group. This process showed a broad substrate scope and excellent selectivity
in which a ligand-controlled functionalization of the unactivated
β-C(sp3)–H bond. In addition, enantioselective
arylation of phenylacetaldehydes was preliminarily explored by utilizing
a bulky chiral transient directing group.
Phenanthrene is an important structural motif in chemistry and materials science, and many synthetic routes have been developed to construct its skeleton. However, synthesis of unsymmetric phenanthrenes remains a challenge. Here, an efficient one-pot tandem reaction for the preparation of phenanthrenes via sequential γ-C(sp 2 )−H arylation, cationic cyclization, dehydration, and 1,2-migration was developed. A wide range of symmetric and unsymmetric phenanthrenes with diversified functional groups were synthesized with good to excellent yields.
Stereoselective [1 + 1 + 4 + 4] dimerization of 1-styrylnaphthols
has been developed by using Selectfluor as the oxidant for the first
time. The reaction was compatible with various functional groups,
giving a class of ethanodinaphtho[b,f][1,5]dioxocines with novel 3D
skeletons. DFT calculations indicate that this method merges an intriguing
stereoselective intermolecular 1 + 1 radical coupling to construct
a bridged C–C bond and then an intramolecular [4 + 4] formal
cycloaddition of the in situ generated o-quinone
methide intermediate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.