作者:Siu Min Tan、Anthony C. Willis、Michael N. Paddon‐Row、Michael S. Sherburn
DOI:10.1002/anie.201510925
日期:2016.2.24
combining the powerful twofold diene‐transmissive Diels–Alder chemistry of [3]dendralenes with the simplicity of enamine formation. On mixing at ambient temperature, a simple dienal condenses with a primary or secondary amine to generate the enamine, a 1‐amino‐[3]dendralene in situ, and this participates as a double diene in a sequence of two Diels–Alder events with separate dienophiles. Overall, four
Preparation of ketones from esters via substituted cyclopropanols
作者:Timour A. Chevtchouk、Vladimir E. Isakov、Oleg G. Kulinkovich
DOI:10.1016/s0040-4020(99)00800-5
日期:1999.11
by chlorination and dehydrochlorination, provides 2-(2,2-diethoxyethyl)-1,3-butadiene that was used as a building block for the synthesis of (±)-ipsenol, (±)-ipsdienol and amitinol - the components of aggregationpheromones of the Ips bark beetles.
The controlled aldol condensation between an aliphatic ketone and an acetaldehyde equivalent remains a challenge. One solution to this evergreen problem consists of the nucleophilic addition of acetylene to the ketone and the subsequent isomerization of the resulting 3-hydroxy-1-alkyne to the corresponding 2-alkenal. So far, however, the latter step could only be executed with acid-insensitive substrates. We now present a milder, three-step method which extends the scope of the procedure considerably. In the first step, the 3-hydroxy-1-alkynes are converted into 2-propynyl ethylene glycol monoethers; these then undergo base-catalyzed cyclization to give the dihydro-1,4-dioxepins, which are hydrolyzed in acidic medium in the third and final step.