Reaction Of Donor-acceptor Cyclopropanes With Acyclic 1,3-diketones To Synthesize 1,6-dicarbonyl Compounds

Donor-acceptor(D-A)cyclopropanes are one of the most useful building blocks in organic synthesis due to their special reactivities and have been widely applied for the synthesis of natural products and biologically active compounds.Ring opening of D-A cyclopropanes with nucleophiles catalyzed by Lewis acids is the most straightforward way to obtain 1,3-bifunctionalized compounds.Both carbon and heteroatom nucleophile additions to D-A cyclopropanes have been well-developed.1,3-Diketone derivatives could be used as both C-and O-nucleophiles due to their nature of easy keto enol tautomerization.The use of 1,3-cyclodiones as O-nucleophiles to add to D-A cyclopropanes had been developed.In this paper,the ring-opening reaction of donor-acceptor cyclopropanes with acyclic 1,3-diketones,which selectively act as C-nucleophiles,had been developed for the synthesis of 1,6-dicarbonyl compounds.1,6-dicarbonyl compounds,representing the formal addition products of the α-position of acetophenone derivatives to donor-acceptor cyclopropanes,were synthesized in two steps via first ring opening of donor-acceptor cyclopropanes with acyclic 1,3-diketones followed by 1,8-diazabicyclo [5.4.0]undec-7-ene(DBU)catalyzed Retro-Claisen-type C-C bond cleavage reactions.In the first step,acyclic 1,3-diketones selectively worked as C-nucleophiles to add to donor-acceptor cyclopropanes.In the second step,the alkyl ketone part of the ring-opening products resulting from unsymmetrical 1,3-diketones was selectively cleaved in the presence of DBU in methanol.The direct additions of acetophenone derivatives to D-A cyclopropanes for the synthesis of 1,6-dicarbonyl compounds are difficult.The method we developed here provides an alternative pathway for the additions of acetophenone derivatives to D-A cyclopropanes under mild conditions for the synthesis of 1,6-dicarbonyl compounds.