Dissecting alkynes: full cleavage of polarized C≡C moiety via sequential bis-Michael addition/retro-Mannich cascade.

The reaction of diaryl ketoalkynes with 1,2-diamino ethane leads to the full scission of the triple bond with the formation of acetophenone and imidazoline fragments. In this transformation, one of the alkyne carbons undergoes formal reduction with the formation of three C-H bonds, whereas the other carbon undergoes formal oxidation via the formation of three C-N bonds (one π and two σ). Computational analysis confirmed that the key fragmentation step proceeds via a six-membered TS in a concerted manner. Both amines are involved in the fragmentation: the N-H moiety of one amine transfers a proton to the developing negative charge at the enolate oxygen, while the other amine provides direct stereoelectronic assistance to the C-C bond cleavage via a hyperconjugative n(N) → σ*(C-C) interaction.

Fast oxy-cope rearrangements of bis-alkynes: competition with central C-C bond fragmentation and incorporation in tunable cascades diverging from a common bis-allenic intermediate.

Fast anionic oxy-Cope rearrangements of 1,5-hexadiyn-3,4-olates can be incorporated into cascade transformations which rapidly assemble densely functionalized cyclobutenes or cyclopentenones via a common bis-allenic intermediate. The competition between fragmentation, 4π-electrocyclic closure, and aldol condensation can be efficiently controlled by the nature of the acetylenic substituents. The rearrangement of bis-alkynes with two hydroxyl substituents opens a conceptually interesting entry in the chemistry of ε-dicarbonyl compounds and suggests a new approach to analogues of rocaglamide/aglafolin.

A novel synthesis of beta-lactam fused cyclic enediynes by intramolecular Kinugasa reaction.

A general synthetic route to beta-lactam-fused enediynes by intramolecular Kinugasa reaction has been successfully developed. The method has widened the scope of Kinugasa reaction in the synthesis of sensitive systems like the one described in this communication.

Synthesis of beta-lactam nucleoside chimera via Kinugasa reaction and evaluation of their antibacterial activity.

Several beta-lactam nucleoside chimeras 1 (cis) and 2 (trans) were synthesized from the corresponding N-propargyl nucleobases via Kinugasa reaction in moderate yields. Initial screening for antibacterial activity against ampicillin sensitive E. coli showed weak activity for the uracil-beta-lactam chimera.