Facile Synthesis of Bicyclic and Tricyclic Skeletons by Cycloisomerizations of Hept-1-en-6-ynes and 4,9-Diheteradodeca-1,11-dien-6-ynes, Followed by [4 + 2] Cycloadditions

Abstract

Keywords: Catalysis / Cycloisomerization / Cyclizations / DielsϪAlder reactions / Enynes / PalladiumPalladium-catalyzed intramolecular cross coupling of various 4-substituted hept-1-en-6-ynes, followed by intermolecular [4 + 2] cycloaddition with methyl acrylate and 2-chloro-2-cyclopropylideneacetate yielded both all-carbon and heteroanalogous bicyclic derivatives 8, 9, 18, 19, and 24 (24−71%). Cycloisomerization of the hydroxymethyl-and hydroxyethyl-substituted hept-1-en-6-ynes 5 and 15, followed by Diels−Alder reaction with methyl acrylate, occurred with intramolecular transesterification to give the tricyclic lactones 11 (37%) and 16 (15%), respectively. Tricyclic systems containing up to three heteroatoms could be obtained from

Allenamides: A Powerful and Versatile Building Block in Organic Synthesis

“…While propargylating N -allylsulfonamide 79 , Meijere 45 obtained a mixture of allenamide 80 and propargyl amide 81 (Scheme 29). …”

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

“…In particular, cycloisomerization of enynes allows one to prepare compounds with exocyclic double bonds and cyclopropanes in a highly selective manner [ 5 – 7 ]. While catalytic transformations of enynes have been investigated in detail, there are only a few examples of similar reactions of dienynes [ 8 – 14 ]. Among dienynes, 1,11-dien-6-ynes 1 are of particular interest, because they are readily available in 1–2 steps from the commercial precursors (e.g., allyl bromides and 1,4-dibromo-2-butyne).…”

“…Among dienynes, 1,11-dien-6-ynes 1 are of particular interest, because they are readily available in 1–2 steps from the commercial precursors (e.g., allyl bromides and 1,4-dibromo-2-butyne). Transformations of 1,11-dien-6-ynes provide an access to highly substituted polycycles [ 8 , 11 – 13 ] ( Scheme 1 ). However, all these transformations require expensive noble metal catalysts with rather sophisticated ligands.…”

Palladium‐Catalyzed Oligocyclizations of 2‐Bromoalka‐1,(n+m+1)‐dien‐(n+1)‐ynes – Influence of Tether Lengths and Substituents on the Outcome of the Reaction (Part II)

“…In this context, several transition metals2 have been utilized to induce different cascade modes to provide a diversity of complex, mostly oligocyclic compounds the access to which, otherwise, would be difficult. Yet, palladium‐catalyzed cascade oligocyclizations of open‐chain substrates, containing several multiple bond fragments, under Heck‐type reaction3 and cycloisomerization conditions4,5 have been among the most extensively studied processes in this area.…”