2 research outputs found
Mechanism and Stereoselectivity of the BINOL-Catalyzed Allylboration of Skatoles
Density functional
theory calculations have been performed to investigate
the binaphthol-catalyzed allylboration of skatoles. The high stereoselectivity
observed for the reaction is reproduced well by the calculations and
was found to be mainly a result of steric repulsions in the corresponding
ZimmermanâTraxler transition states. The role of the additive
MeOH in enhancing the stereoselectivity was also investigated and
is suggested to promote the formation of less reactive allylboronic
ester intermediates, thereby suppressing the formation of allylboroxine
species, which undergo the facile racemic background reaction
Scalable, Chromatography-Free Synthesis of Alkyl-Tethered Pyrene-Based Materials. Application to First-Generation âArchipelago Modelâ Asphaltene Compounds
In
this paper, we report a highly efficient, scalable approach
to the total synthesis of conformationally unrestricted, electronically
isolated arrays of alkyl-tethered polycyclic aromatic chromophores.
This new class of modular molecules consists of polycyclic aromatic
âislandsâ comprising significant structural fragments
present in unrefined heavy petroleum, tethered together by short saturated
alkyl chains, as represented in the âarchipelago modelâ
of asphaltene structure. The most highly branched archipelago compounds
reported here share an architecture with first-generation dendrimeric
constructs, making the convergent, chromatography-free synthesis described
herein particularly attractive for further extensions in scope and
applications to materials chemistry. The syntheses are efficient,
selective, and readily adaptable to a multigram scale, requiring only
inexpensive, âearth-abundantâ transition-metal catalysts
for cross-coupling reactions and extraction and fractional crystallization
for purification. This approach avoids typical limitations in cost,
scale, and operational practicality. All of the archipelago compounds
and synthetic intermediates have been fully characterized spectroscopically
and analytically. The solid-state structure of one archipelago model
compound has been determined by X-ray crystallography