tandem substitution/Krapcho reaction is reported for the facile synthesis of α-fluorinated esters and sulfones, which utilizes the byproduct salt formed in the substitution step as an indispensible reagent to facilitate the Krapcho reaction step. This represents the first sustainable tandem reaction that internally recycles the waste salt formed in the upstream step as the reagent for the downstream step
of dienynes was investigated using cobalt-based catalysts. Substrates without substitution on alkyne moiety were found to react under thermal activation. The use of a cobalt salt as catalyst made reactions cleaner by limiting the formation of byproducts. Cycloadditions with dienynes possessing a substituent on the alkyne pattern occurred only in presence of a cobalt catalyst which displayed a moderate
ylides from glycine pyrazoleamides and allyl bromides were achieved by employing a chiral N,N′-dioxide/MgII complex as the catalyst. This protocol provided a facile and efficient synthesis route to a series of anti-α-amino acid derivatives in good yields with high stereoselectivities. Moreover, a possible catalytic cycle was proposed to illustrate the reaction process and the origin of stereoselectivity
Unified total synthesis of the natural products endiandric acid A, kingianic acid E, and kingianins A, D, and F
作者:S. L. Drew、A. L. Lawrence、M. S. Sherburn
DOI:10.1039/c5sc00794a
日期:——
A measure of the strength of a synthetic strategy is its versatility: specifically, whether it allows structurally distinct targets to be prepared. Herein we disclose a unified approach for the total synthesis of natural products of three distinct structuraltypes, all of which occur naturally as racemic mixtures. The point of divergence involves the terminal alkylation of a conjugated tetrayne, and
4-dienylation/Michael addition/π–σ–π isomerization/allylic alkylation. A broad array of enantioenriched architectures having fused and spirocyclic frameworks are constructed in moderate to excellent yields and stereoselectivity. Notably, the intrinsic intramolecular Diels–Alder reaction pattern of the dienylated intermediates is well reversed via Pd(0)−π–Lewis base catalysis.