Studies On The Radical Cyclization And Metal-catalyzed Reaction Of Diarylmethylenecyclopropa[b]Naphthalenes

The development of novel reactions with high regio-and stereoselectivity for construction of useful molecules is a hot topic in organic synthesis. Recently, we have witnessed tremendous growth in the number of efficient strategies converting easily accessible starting materials to complex and interesting organic molecules.Methylenecyclopropanes (MCPs) are readily accessible but highly strained carbocyclic molecules that have served as useful building blocks in organic synthesis. In the past decades, mounting attention has been paid to the transition metal-or Lewis acid-catalyzed reactions of MCPs, which have been employed for the construction of complex and interesting organic molecules. However, an attractive but often troublesome feature of MCPs is their multi-forms of reactivities leading to the formation of a variety of different products. During our systematic study of MCPs chemistry, we have been interested in the chemistry of its analogues, alkylidenebenzocycloproparenes. Because of the unusual structure of alkylidenebenzocycloproparenes, incorporating within the one molecule of a triafulvene, a [3]radialene and the cycloproparene, they have attracted much attention from physical, theoretical and synthetic viewpoints.We have developed the following reactions:1. We have developed manganese(Ⅲ) acetate-mediated free radical cyclization of diarylmethylenecyclopropa[b]naphthalenes with nucleophiles such as carboxylic acid and sulfonic acid, providing an efficient method for the synthesis of 1,2-benzanthracenes in moderate to good yields under mild conditions. In addition, after several steps of simple and routine operations, the obtained1,2-benzanthracenes bearing an acetoxy group could be easily converted to structurally more sophisticated1,2-benzanthracene derivatives, which are not easily accessible yet potentially useful candidates for materials science.2. We have developed the first palladium-catalyzed highly regioselective [3+2] cycloaddition reaction of diarylmethylenecyclopropa[b]naphthalenes with alkenes or alkynes, providing an efficient method for the synthesis of1(3)-alkylidene-2,3-dihydro-1H-cyclopenta[b]naphthalenes or1-alkylidene-lH-cyclopenta[b]naphthalenes with good regioselectivity under mild conditions.3.We have developed a ligand-controlled highly regioselective ring-opening coupling reaction of diarylmethylenecyclopropa[b]naphthalenes with Grignard reagents, providing differently substituted β-vinylic naphthalenes in moderate to excellent yields. When Pd(PPh3)2Cl2was employed, the aromatic group from the Grignard reagent regioselectively coupled with the olefin unit after the ring-opening of three-membered ring. This selectivity may result from the steric hindrance of the PPh3groups in the palladacyclobutene intermediates. The result was supported by in-situ NMR experiments. Interestingly, when Pd(OAc)2was used, the regioselectivity was totally switched and the aromatic group coupled to the naphthyl ring probably.4. We have developed a nickel-catalyzed atom-economical and highly selective C-P bond cleavage of phosphines involving ring-opening coupling reaction of diarylmethylenecyclopropa[b]naphthalenes. The reaction takes place via a catalytic cycle invoving oxidative addition of nickel(0) with the carbon-carbon single bond in the three-membered ring of diarylmethylenecyclopropa[b]naphthalenes, cleavage of the C-P bond and migration of the ary group of the phosphines, consequently providing a new type of bulky phosphines in excellent yields.