Reactions of 5,6-Dilithioacenaphthene-N,N,N',N'-Tetramethyl-1,2-ethanediamine Complex with α-Diketones. I. cis-Directing 1:1 Cyclic Additions with Acyclic and Cyclic α-Diketones and Related Compounds

Article abstract of DOI:10.1246/bcsj.54.3020

The title complex (3) is readily generated from 5,6-dibromoacenaphthene with butyllithium and the diamine in ether at -10-0 deg C.The reaction of 3 with biacetyl gave cis-1,2,5,6-tetrahydro-1,2-dimethylcyclopent-acenaphthylene-1,2-diol but no trans-isomer, whereas the reaction of pyracenequinone (PYQ) with methylmagnesium bromide gave both the cis- and trans-diols.The reactions of 3 with acenaphthenequinone and PYQ also gave cis-diols.On treatment with phenylboronic, these cis-diols quantitatively yielded the corresponding cyclic esters.The diols and their derivatives tend to form crystalline molecular compounds with solvent molecules.The stereoselectivity of the cyclic addition between 3 and the acyclic α-diketone can be best explained in terms of five-membered chelate-ring formation in a transition state.