Radical-Mediated Synthesis of Racemic Deoxypodophyllotoxin and Related Lignans
作者:Philippe Renaud、Tanja Kolly-Kovač
DOI:10.1055/s-2005-865358
日期:——
An approach for the synthesis of lignans related to the podophyllotoxin family is reported. The key reaction is a highly diastereoselective iodoacetal cyclization under iodine atom transfer conditions followed by a homolytic aromatic substitution. The second aromatic ring is introduced at a laterstage via addition of aryllithium to an aryl ketone. A novel and very mild method for the deoxygenation
The synthesis of azoacetylenes (=dialkynyldiazenes) 1 and 2 has been investigated. They represent a still elusive class of chromophores with potentially very interesting applications as novel bistable photochemical molecular switches or as antitumor agents (Fig. 1). Our synthetic efforts have led us alongside three different approaches (Scheme 1). In a first route, it was envisioned to generate the
Lewis Acid-Activated Reactions of Silyl Ketenes for the Preparation of α-Silyl Carbonyl Compounds
作者:Sarah M. Mitchell、Yuanhui Xiang、Rachael Matthews、Alexis M. Amburgey、Emily B. Pentzer
DOI:10.1021/acs.joc.9b01859
日期:2019.11.15
Silyl-substituted ketenes are attractive molecular building blocks due to their stability and ease of storage, as opposed to unstable alkyl and aryl ketenes. To better understand the reactivity of silyl ketenes and, in turn, their use in the preparation of highly functionalized small molecules, the reaction of silyl ketenes with different nucleophiles was studied. The addition of alcohol, amine, or
<i>C</i><sub>2</sub>-Symmetric Cu(II) Complexes as Chiral Lewis Acids. Catalytic, Enantioselective Cycloadditions of Silyl Ketenes
作者:David A. Evans、Jacob M. Janey
DOI:10.1021/ol016096z
日期:2001.6.1
[reaction: see text] C(2)-Symmetric bis(oxazoline)-Cu(II) complexes (4a-g) catalyze the enantioselective [2 + 2] cycloaddition between (silyl)ketenes and chelating carbonyl substrates. A range of substituted beta-lactones can be produced in excellent yields and selectivities. It was also found that (trimethylsilyl)ketene (1) may also undergo a highly selective hetero Diels-Alder reaction with beta