5 research outputs found
Type 1 Ring-Opening Reactions of Cyclopropanated 7‑Azabenzonorbornadienes with Organocuprates
The first nucleophilic
ring-opening reactions of cyclopropanated
7-azabenzonorbornadienes have been achieved using organocuprates.
Tricyclic or tetracyclic γ-lactams were obtained as the sole
product in good yields of up to 98% when alkoxycarbonyl groups occupied
the N-substituent position. Successful conversions to lactams were
observed for primary, secondary, tertiary, and aromatic nucleophiles,
as well as for a variety of substrates functionalized on the benzene
ring. A possible mechanism for these transformations is discussed
Synthesis of Cyclopropanated [2.2.1] Heterobicycloalkenes: An Improved Procedure
<div><p></p><p>A safer and improved method to our previous report on palladium-catalyzed cyclopropanation of heterobicyclic alkenes has been developed. By using THF as the solvent and a more dilute aqueous NaOH solution for the generation of diazomethane from Diazald®, cyclopropanation could be achieved smoothly with minimal adjustment over the course of reaction. 7-Oxabicyclic substrates with bulky C1 or C2 groups, as well as 2,3-diazabicyclic substrates with various N-substituents effectively underwent cyclopropanation. Using this methodology, yields to previously reported products were markedly increased, and 10 new cyclopropanated [2.2.1] heterobicyclic products were prepared. In addition, this work accounts for the first reported cyclopropanation of 2,3-diazabicyclic alkenes, which all gave excellent yields of >90%.</p></div
Type 1 Ring-Opening Reactions of Cyclopropanated 7‑Oxabenzonorbornadienes with Organocuprates
For the first time, nucleophilic
ring-openings of cyclopropanated
7-oxabenzonorbornadiene were investigated, providing a novel approach
to the preparation of 2-methyl-1,2-dihydronaphthalen-1-ols. Satisfactory
yields (up to 95%) were achieved using <i>n</i>-Bu<sub>2</sub>CuCNLi<sub>2</sub> as the nucleophile and Et<sub>2</sub>O as the
solvent. The reaction demonstrated successful incorporation of primary,
secondary, tertiary and aromatic nucleophiles, as well as ring-openings
of substrates bearing arene substituents and C1-bridgehead substituents.
A generalized mechanism for these transformations is also proposed
Ruthenium-Catalyzed Asymmetric [2 + 2] Cycloadditions between Chiral Acyl Camphorsultam-Substituted Alkynes and Bicyclic Alkenes
Ruthenium-catalyzed asymmetric [2
+ 2] cycloadditions between chiral
acyl camphorsultam-functionalized alkynes and bicyclic alkenes were
examined, providing adducts with complete <i>exo</i> stereoselectivity
in good overall yield and enantioselectivity (up to 99% and 166:1,
respectively), as well as appreciable diastereoselectivity (up to
163:1). The diastereoselectivity showed dependence on the solvent
and temperature, as well as on the substitution pattern of the reacting
alkyne and bicyclic alkene components. In general, higher diastereoselectivities
were observed for reactions conducted in ethereal solvents and at
lower temperatures between <i>N</i>-propynoyl camphorsultams
and bicyclic alkenes
Ruthenium-Catalyzed [2 + 2] Cycloadditions between Norbornene and Propargylic Alcohols or Their Derivatives
Diastereoselective ruthenium-catalyzed
[2 + 2] cycloadditions of
norbornene and propargylic alcohols or their derivatives were investigated.
The cycloadditions were found to be highly stereoselective, giving
exo cycloadducts in moderate to excellent yields with diastereoselectivities
up to 92:8. When a chiral propargylic alcohol was used in the cycloaddition,
up to 80% ee of the [2 + 2] cycloadducts was observed after oxidation
of the alcohol