Thermal Intramolecular [2+2] Cycloaddition of Allenenes and Allenynes: Diastereoselective Access to Bicyclic Nitrogen Heterocycles

Abstract

Squaring the circle: A route to bicyclo[4.2.0]octane derivatives has been developed by the [2+2] cycloaddition of allenenes or allenynes. The thermal intramolecular [2+2] cycloaddition of simple allenes 1 with an additional multiple bond leads to direct and regioselective formation of the distal adducts 2 in good to excellent yields.

Gold-Catalyzed Cycloisomerization of 1,5-Allenynes via Dual Activation of an Ene Reaction

“…1,2,3 These reactions involving Rh, Pd, or Pt are generally postulated to proceed via metallacyclopentene intermediates, inherently involving an increase in the formal oxidation state of the metal. 1,4 On the other hand, gold(I)-catalyzed enyne 5 and some related 1,6-allenyne cycloisomerization reactions 6 are proposed to proceed without a change in the formal oxidation state of the catalyst.…”

Component-Selective and Stereocontrolled One-Step Three-Component Reaction among Aldehydes, Amines, and Allenyl Boronic Acids or Allenyl Pinacolboronates

“…The parent allenyl boronic acid 10 and its boronates have been known for some time, , while the preformed tartrate derivatives were shown to add readily to aldehydes and ketones in a practical and enantioselective manner. − Despite their ability to undergo facile γ-intramolecular addition to aldehydes, the reported chemistry demonstrates that allenyl boron compounds can also add preferably to certain in situ adjacent iminium salts to produce allenyl and alkynyl amines and amino acids. The products of this one-step process are multifunctional allenyl and propargyl amine derivatives, which are versatile and valuable building blocks for synthetic and medicinal applications …”

Palladium-catalysed formation of vicinal all-carbon quaternary centres via propargylation

“…In fact, the absolute configuration of the chiral propargylation products ( S )- 3ga , ( S )- 3gd , ( S )- 3gg and ( S )- 3gj has been established on the basis of an X-ray single-crystal diffraction study of this product. (2) The 1,6-allenyne derivative 3ja and ( S )- 3ga could go through a thermal [2+2] reaction3435 to construct the tricyclic product 13ja containing two highly strained four-membered rings and bicyclic product ( S )- 13ga containing one highly strained four-membered ring in very high yields. (3) In addition, the hydrogenation or semi-hydrogenation of the carbon–carbon triple bond in ( S )- 3gj afforded saturated ( S )- 14 under 15 mol% of Pd/C catalyst or ( S,Z )- 15 with a Z -double bond under 10 mol% of the Lindlar catalyst, respectively3637.…”