45 research outputs found
Copper(I) Halide Promoted Diastereoselective Synthesis of Chiral Propargylamines and Chiral Allenes using 2‑Dialkylaminomethylpyrrolidine, Aldehydes, and 1‑Alkynes
Copper bromide promoted reactions of aldehydes, 1-alkynes,
and chiral 2-dialkylaminomethylpyrrolidine at 25 °C give the
corresponding chiral propargylamine derivatives in up to 96% yield
and 99:1 dr that are readily converted to the corresponding disubstitued
chiral allenes in up to 81% yield and 99% ee upon reaction with CuI
in dioxane at 100 °C
Synthesis of Phenols and Aryl Silyl Ethers via Arylation of Complementary Hydroxide Surrogates
Two transition-metal-free methods to access substituted phenols via the arylation of silanols or hydrogen peroxide with diaryliodonium salts are presented. The complementary reactivity of the two nucleophiles allows synthesis of a broad range of phenols without competing aryne formation, as illustrated by the synthesis of the anesthetic Propofol. Furthermore, silyl-protected phenols can easily be obtained, which are suitable for further transformations
Control of Five Contiguous Stereogenic Centers in an Organocatalytic Kinetic Resolution via Michael/Acetalization Sequence: Synthesis of Fully Substituted Tetrahydropyranols
An organocatalytic kinetic resolution
of racemic secondary nitroallylic
alcohols via Michael/acetalization sequence to give fully substituted
tetrahydropyranols is described. The process affords the products
with high to excellent stereoselectivities (up to 19.9:1.5:1 dr and
98% ee). The highly enantioenriched, less reactive (<i>S</i>)-nitroallylic alcohols <b>3</b> were isolated with good to
high chemical yields (30–44%). The synthetic application of
the resolved substrate is shown toward the synthesis of enantioenriched
(+)-(2<i>S</i>,3<i>R</i>)-3-amino-2-hydroxy-4-phenylbutyric
acid
Enantioselective Synthesis of Functionalized Polycarbocycles via a Three-Component Organocascade Quadruple Reaction
An efficient organocascade quadruple
reaction was conducted to synthesize a functionalized spiropolycyclic
scaffold in high chemical yields (43–80%) and excellent levels
of stereoselectivity (up to >19:1 dr and 99% ee). The quadruple
reaction proceeded smoothly between 1,3-indanedione and aromatic aldehydes
with concomitant desymmetrization of prochiral 4-substituted cyclohexanones
through the Knoevenagel/Michael/aldol/aldol reaction sequence catalyzed
by a bifunctional thiourea catalyst. Two of the formed products were
transformed into spirocyclic epoxides containing four contiguous quaternary
centers
Doyle–Kirmse Reaction on Alkynyl Hydrazone Carboxylates: Synthesis of 1,4-Allenyne and 1,5-Enyne Thioaryl Carboxylates
The first Doyle–Kirmse reaction
on alkynyl diazoacetates
using allyl/propargyl sulfides is reported. The development provides
diversified 1,5-enyne and 1,4-allenyne thioaryl carboxylates in good
yields under ligand-/additive-free AuCl and Rh2(OAc)4 catalysis, respectively (48 examples, up to 96% yield). The
study demonstrated the dual role of allyl sulfide as a ligand and
substrate. Also, we have exemplified various synthetic modifications
of the products to showcase the utility of different functional groups
Highly Enantioselective Synthesis of Chiral Allenes by Sequential Creation of Stereogenic Center and Chirality Transfer in a Single Pot Operation
Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities