Ethoxyacetylene: A useful building block for the organocopper(I) mediated synthesis of 1,4-diketones

Copper-Catalyzed Regioselective and Stereoselective Coupling of Grignard Reagents with Pent-1-en-4-yn-3-yl Benzoates: A Shortcut to ( Z) -1,5-Disubstituted Pent-3-en-1-ynes from Accessible Starting Materials

Copper-catalyzed coupling of Grignard reagents with pent-1-en-4-yn-3-yl benzoates occurs regioselectively at the terminal alkenyl carbon rather than the alkynyl site, leading to the stereoselective formation of unexpected ( Z) -1,5-disubstituted pent-3-en-1-ynes without generation of the initially expected alkenyl allene products. By using easily accessible starting materials, this reaction can provide direct access to thermodynamically unfavorable Z-configured enynes, which widely exist in many bioactive natural products, such as the anti-inflammatory components in henna.

Regio- and Stereoselective Anti-Carbozincation of Alkynyl Ethers Using ZnBr2 toward (Z)-β-Zincated Enol Ether Synthesis

(Z)-β-Aryloxyalkenylzincs are synthesized stereoselectively via anti-carbozincation among alkynyl ethers, silyl ketene acetals, and ZnBr₂. X-ray analysis revealed the structure of the zinc species is a mononuclear two-coordinate dialkenylzinc that is transformed into functionalized enol ethers as a single isomer in the reaction of various electrophiles.

Tandem Inter [4 + 2]/Intra [3 + 2] Cycloadditions of Nitroalkenes. The Bridged Mode (beta-Tether)

A new variation of the tandem inter [4 + 2]/intra [3 + 2] cycloaddition of nitroalkenes has been developed. This method involves the Lewis acid-promoted [4 + 2] cycloaddition of nitro olefins 12 with 1-alkoxy-1,4-dienes 3. The resulting nitronates 13, bearing a C(5) tethered dipolarophile, undergo thermal, intramolecular [3 + 2] cycloaddition to afford stable tricyclic nitroso acetals 14, which can be subsequently reduced to unveil a new carbocycle 16. Thus, in three steps, highly functionalized aminocyclopentanes can be stereoselectively constructed in high yield.