A simple and mild process was developed for the highly stereoselective synthesis of halogenated bicyclic [4.3.0] and [3.3.0] γ-lactams, possessing four stereocenters, from easily available cyclic 2-enynamides. The reaction required only an inexpensive iron(II) halide under dry air and was tolerant of aryl, heteroaryl, and alkyl groups at the alkyne terminus.

A simple and efficient FeCl(3)-promoted cyclization/chlorination of cyclic tosylamine-tethered 8-aryl-2-en-7-yn-1-ols was observed. The reaction proceeded instantaneously at 23 °C in air to afford (Z)-4-(arylchloromethylene)-substituted azaspirocycles in good to excellent yields. This transformation can also be applied to the synthesis of spirocarbocyclic analogues from cyclic 8-aryl-2-en-7-yn-1-ols and FeCl(3).

A facile and efficient N-to-C allyl shiftaza-Prins cyclization sequence of cyclic N-2-en-4ynyl-N-1-ynylamides is promoted by iron(III) chloride, generating chloro-containing bridged bicyclic enamines in minutes and in high yields. This reaction involves an unprecedented formation of a ketenimine via Fe(III)-mediated N-to-C allyl rearrangement, followed by aza-Prins cyclization. This sequence can also be applied to the generation of brominated cyclobutenamine derivatives using Fe(III) bromide and N-propargyl-N-1-ynylamides.

An efficient stereoselective synthesis of 7‐(E)‐arylidene‐2‐chloro‐6‐azabicyclo[3.2.1]octanes is described. The aluminum chloride‐promoted cyclization/chlorination of six‐membered ring 3‐enynamides enables a straightforward approach to the 6‐azabicyclo[3.2.1]octane nucleus that is incorporated in many biologically active compounds. Acid treatment of the resultant chlorinated arylideneazabicyclooctanes furnishes 3‐alkanoyl‐4‐chlorocyclohexanamines in excellent yields and high stereoselectivity.magnified image

A series of substituted nitrogen-containing 9-membered epoxy vinyl ethers has been constructed from easily available 5-aza-2,3-epoxy-7-yn-1-ols. Attack of the hydroxyl group onto the gold(I)-activated alkyne gave the postulated 9-membered allylic vinyl ether gold intermediate which underwent protodeauration affording the 9-membered epoxy vinyl ethers.Scheme I Gold-catalyzed Claisen-type rearrangements of nitrogen-containing 2-en-7-yn-1ols Scheme II A Postulated reaction path for the formation of cis-3-aroyl-4-vinylpyrrolidine (3) from (Z)-8-aryl-5-azaoct-2-en-7-yn-1-ol (1)