Copper(I)-Catalyzed Intramolecular Asymmetric [2 + 2] Photocycloaddition. Synthesis of Both Enantiomers of Cyclobutane Derivatives

Abstract

[reaction: see text] A simple approach for asymmetric induction in Cu(I)-catalyzed [2 + 2] photocycloaddition, where asymmetric catalysts or chiral auxiliaries were inefficient, has been developed using the concept of chirality transfer from the readily available 2, 3-di-O-cyclohexylidine-(R)-(+)-glyceraldehyde. An anion-induced cleavage of the tetrahydrofuran ring of the resulting oxa-bicyclo[3.2.0]heptanes led to a convenient access to the synthetically useful cis-1,2-disubstituted cyclobutanes in enantiomerically pure form.

Concepts of Stereoselective Photochemistry and a Case Study: the Paterno-Buchi Reaction

“…Introducing chiral auxiliary in the molecule making more simple the attack on a prochiral face of the substrate; examples have been reported on 2+2 cycloadditons (Scheme 12) [42][43][44][45][46][47][48][49][50], and in photocyclization (Norrish Type II reaction) [51,52]. 2.…”

Photocycloaddition in Natural Product Synthesis

“…The naturally occurring cyclobutane monoterpene grandisol, an important component in the sexual attracting pheromone of the cotton boll weevil has attracted considerable interest in this regard 20–29. Ghosh and co‐workers' approach towards both enantiomers of grandisol relies on chirality transfer at C2 from the readily available diene 1 to yield the cis ‐1,2‐disubstituted cyclobutane 2 (Scheme ) 30. Irradiation of an ether solution of the diene 1 in the presence of 20–25 mol‐% of copper(I) trifluoromethanesulfonate occurred efficiently to furnish 2 in 82 % yield.…”

Total Synthesis of the Marine Polyketide (−)-Gracilioether F

“…The masked diol in 10 will be the source of the epoxide ring. Compound 10 in turn will be available from d -mannitol-derived known unsaturated ester 11 which was employed by us earlier in several chiral syntheses . The present route will thus accomplish synthesis of gracilioethers in enantiomerically pure form, unlike the other reported approaches which provided only the racemates.…”