Ultrasound in organic synthesis 16. Optimisation of the conjugate additions to α,β-unsaturated carbonyl compounds in aqueous media.

Total Synthesis of Schilancitrilactones B and C

“…Deprotection of 26 was achieved using trifluoroacetic acid and gave the acid 27 in 93 %y ield (two steps). By using the method (CuI, Zn under ultrasound) for conjugate additions in aqueous media discovered by Luche et al, [16] we were pleased to observe the cyclization product 31 in 55 %yield, together with the isomer 31' in 4% yield. [12] Thea bsolute configuration of 28 was determined by X-ray crystallographic analysis.T he cyclohexene ring in 28 was oxidatively cleaved by ozonolysis and the resulting dialdehyde 29 was directly subjected to intramolecular aldol condensation, thus yielding the ring-closed unsaturated aldehyde 8 (80 %y ield for two steps).…”

“…[5] Herein we report our efforts on developing anew strategy to solve the chemical synthesis of 1 and 2,a nd apathway for the synthesis of their analogues and derivatives for medicinal studies.Our retrosynthetic analysis is shown in Scheme 1. Theb uilding blocks 4, 7,a nd 8 could be prepared from the commercially available compounds citraconic anhydride (16), l-carvone (9), and 1,3-cyclohexadiene (19), respectively. [6] Thec ompound 6 was further deconstructed at the C10ÀC19 bond into the two simple building blocks 7 and 8,w hich could be put together by an aldol reaction.…”

Navigating the Chiral Pool in the Total Synthesis of Complex Terpene Natural Products

“…Straightforward aldol coupling between the lithium enolate of 368 and aldehyde 369 cleanly generated 370 in excellent yield (86%). Alcohol dehydration of 370 (CuCl 2 , EDC) and subsequent conjugate addition of the alkyl iodide center (CuI/Zn) 432 to the resulting unsaturated system zipped up the seven-membered ring, affording pentacycle 371 as the major product. Notably, conventional tin-based and modern photoredox-mediated radical cyclizations failed to elicit this seven membered ring-forming process.…”

Desenvolvimento sustentável e química verde

“…O efeito de ultra-som é importante principalmente em reações Luche e colaboradores demonstraram que haletos de alquila reagem com aldeídos e cetonas α,β-insaturados, levando aos produtos de adição quando na presença de zinco-cobre em água ou solventes duplos sobre ação de ultra-som [68][69][70] . Recentemente, Suárez e colaboradores reportaram alguns exemplos de adições conjugadas estereosseletivas de iodetos induzidas por zinco-cobre a sistemas carbonílicos α,β-insaturados quirais (Esquema 22) 71 .…”