Chiral Phosphoric Acid-Catalyzed Enantioselective and Diastereoselective Spiroketalizations
摘要:
Catalytic enantioselective and diastereoselective spiroketalizations with BINOL-derived chiral phosphoric acids are reported. The chiral catalyst can override the inherent preference for the formation of thermodynamic spiroketals, and highly selective formation of nonthermodynamic spiroketals could be achieved under the reaction conditions.
Chiral Phosphoric Acid-Catalyzed Enantioselective and Diastereoselective Spiroketalizations
摘要:
Catalytic enantioselective and diastereoselective spiroketalizations with BINOL-derived chiral phosphoric acids are reported. The chiral catalyst can override the inherent preference for the formation of thermodynamic spiroketals, and highly selective formation of nonthermodynamic spiroketals could be achieved under the reaction conditions.
The carboazidation of chiralallylsilanes has been investigated by varying the nature of the substituents at the silicon center and on the carbon framework. The influence of temperature and the nature of the sulfonyl azide, as well as the stereochemistry of the remote stereogenic center, on the 1,2-diastereocontrol of the process were considered. Good to excellent levels of diastereocontrol were generally
Pd<sup>II</sup>-Catalyzed Spiroketalization of Ketoallylic Diols
作者:Jean A. Palmes、Paulo H. S. Paioti、Leonardo Perez de Souza、Aaron Aponick
DOI:10.1002/chem.201301723
日期:2013.8.26
at 0 °C, these dehydrative cyclization reactions require only mild conditions to produce vinyl‐substituted spiroketals in high yields after brief reaction times with water as the only byproduct. Using this method, the stereochemical information embedded at the nucleophile is transmitted “down‐the‐chain” and efficiently sets the stereochemistry at both the anomeric carbon atom and the newly formed allylic
efficient 12‐step synthesis of the marine alkaloid (−)‐nakadomarin A has been accomplished. The key advanced intermediate, a tetracyclic ketone derivative, was constructed in just seven steps using a sequence that includes an asymmetric Pauson–Khand reaction, an Overman rearrangement reaction, a ring‐closing metathesis reaction, and an amination reaction. Late introduction of the furan ring during the synthesis
The PdII-catalyzed tandem cyclization of chiral allylic alcohols possessing an internal epoxide and a terminal alcohol provided a contiguous THF–THP and THF–THP ring units stereospecifically. The cyclizations take place via a 5-exo-tet-5-exo-trig mode, however, the cyclization of methyl substituted epoxy diols proceeded via 6-endo-tet-6-exo-trig fashion in a part to construct the oxygen-fused THP–THP