THESIS
2018
xv, 96 pages : illustrations ; 30 cm
Abstract
Over the past decades, quinone methides (QMs) have been widely employed as a
kind of useful building blocks in the synthesis of natural products and biologically
active molecules. Their typical reactivity is reviewed in Chapter 1. Because of their
extremely high reactivity, early studies on QMs mainly focused on the pre-synthesized
isolable ones. To address this limitation, many strategies to in situ generate QMs have
been developed. Recently, a series protocols employing ortho- or para-hydroxybenzyl
alcohols to in situ generate QMs in the presence of a catalytic amount of Brønsted acids
have been reported. In this thesis, two new methods using this strategy to generate QMs
for the synthesis useful molecules have been developed.
In Chapter 2, a process of synthesizing chiral β,...[
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Over the past decades, quinone methides (QMs) have been widely employed as a
kind of useful building blocks in the synthesis of natural products and biologically
active molecules. Their typical reactivity is reviewed in Chapter 1. Because of their
extremely high reactivity, early studies on QMs mainly focused on the pre-synthesized
isolable ones. To address this limitation, many strategies to in situ generate QMs have
been developed. Recently, a series protocols employing ortho- or para-hydroxybenzyl
alcohols to in situ generate QMs in the presence of a catalytic amount of Brønsted acids
have been reported. In this thesis, two new methods using this strategy to generate QMs
for the synthesis useful molecules have been developed.
In Chapter 2, a process of synthesizing chiral β,β-diaryl-α-amino acid derivatives via
asymmetric addition of azlactones to p-QMs is described. The process is realized by
using a suitable chiral phosphoric acid to not only help generating p-QMs in situ, but
also catalyze the conjugate addition step in a stereocontrolled fashion. Although
excellent enantioselectivity can be obtained in this process, diastereoselectivity is low
throughout the condition screening. After substantial efforts, the problem is solved by
one-pot protection of the free hydroxyl group in the product.
Chapter 3 describes a novel C6-alkylation of indoles by employing different QMs as
alkylating reagents. N-Alkylated indoles, which are considered to be kinetic products,
are observed in some cases and then are converted to C6-alkylated products, which are
the thermodynamic ones. Mechanistic study shows that the C–N bond foramtion is a
reversible process while C–C bond formation is irreversible. This metal-free protocol
enriches the toolbox of indole functionalization.
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