The synthesis of nitrogen heterocycles via the intramolecular Khand reaction: formation of tetra- and hexa-hydrocyclopenta[c]pyrrol-5(1H)-ones and hexahydro-6H-2-pyrindin-6-ones

Abstract

Azabicyclo[3.3.0]octenones and azabicyclo[4.3.0] nonenones have been obtained by cyclisation of hexacarbonyldicobalt complexes of aza-heptenynes and -0ctenynes respectively. A n unusual feature of the cyclisation of N-acyl-4-azahept-1 -en-6-ynes is the extensive formation of the reduced products, N-acyl -3-aza bicyclo [ 3.3.01 octan -7 -ones under most reaction conditions.The first example of an intramolecular Khand reaction was the formation of the 2-oxabicylononenone (1) from the cobalt complex of pent-4-ynyl vinyl ether. Numerous 3-oxabicyclo-[3.3.3]oct-5-en-7-ones[ 5-oxa-4,5,6,6a-tetrahydro-1 H-pentalen-2-ones] have subsequently been efficiently synthesised in the same way from variously substituted ally1 prop-2-ynyl ether^.^-^

Synthesis of Cyclopropylpyrrolidines via Reaction of N-Allyl-N-propargylamides with a Molybdenum Carbene Complex. Effect of Substituents and Reaction Conditions

“… Following the general procedure, a solution of N -allylbenzamide (2.46 g, 15.3 mmol) in THF (50 mL) was treated with NaH (550 mg, 80% dispersion in mineral oil, 18.3 mmol) and propargyl bromide (80% in toluene, 5.11 mL, 45.8 mmol) to give 13b (2.59 g, 85%). Spectral data for 13b was in agreement with that previously reported …”

Cobalt Carbonyl-Mediated Carbocyclizations of Enynes: Generation of Bicyclooctanones or Monocyclic Alkenes

“…Isolation and identification of cyclopentanones under the PKR conditions at unusually high temperatures were first accounted by Serratosa . Pauson later reported that cyclopentanones had been frequently encountered as trace byproducts in their earlier cyclization studies . To date only three studies that exploited the exclusive formation of saturated ketones are available (Table ).…”

Cascade Reactions Involving Pauson—Khand and Related Processes

“…Other ways of labilizing CO ligands consist of irradiating the complex with ultraviolet light [63], ultrasounds [64] or microwaves [65,66]. The latter conditions seem to shorten reaction times remarkably, though results are not spectacular with respect to conversions.…”