PALLADIUM-CATALYZED REDUCTIVE COUPLINGS OF ORGANIC HALIDES WITH 7-HETEROATOM NORBORNADIENES - NEW SYNTHETIC METHODS FOR SUBSTITUTED ARYLS AND CIS-1,2-DIHYDRO-1-NAPHTHYL ALCOHOLS AND CARBAMATES

PdCl2(PPh(3))(2) in the presence of zinc metal powder and triethylamin e catalyzes coupling reactions of 7-aza- and 7-oxanorbornadienes, dime thyl -azabicyclo[2.2.1]2,5-heptadiene-2,3-dicarboxylate (4a) and dimet hyl axabicyclo[2.2.1]-2,5-heptadiene-2,3-dicarboxylate (4b), with orga nic iodides (RI) to give the substituted aryls 1,2-(MeO(2)C)(2)-4-RC(6 )H(3) (5) in fair to good yields. Under similar reaction conditions, 7 -carbomethoxy-7- azabenzonorbornadiene (4c) and 1,4-epoxy-1,4-dihydron aphthalene (4d) react with organic iodides to afford the 2-substituted naphthalenes 2-RC(10)H(7) (7) and the cis-dihydro products methyl N-( cis-1,2-dihydro-1-naphthyl)carbamate (cis-1,2-H-2-1-(MeO(2)CHN)-2-RC(1 0)H(6), (8)) and cis-1,2-dihydro-1-naphthol (cis-1,2-H-2-1-(OH)-2-RC(1 0)H(6), (9)), respectively. To improve the product yields of the last two cis-dihydro compounds, a modified system, Pd(PPh(3))(2)Cl-2-ZnCl2- Et(3)N-Zn, was used to catalyze the reactions of 4c,d, 1,4-dihydro-5, 8-dimethoxy-1,4-epoxynaphthalene (4e), and ihydra-5,8-dimethoxy-1-meth yl-1,4-epoxynaphthalene (4f) with organic halides. These catalytic rea ctions produce the corresponding derivatives of 8 and 9 cis-1,2-H-2-1- (OH)-2-R-5,8-(MeO)(2)C10H4 (11) and cis-1,2-H-2-1-(OH)-2-R-4-Me-5,8-(M eO)(2)C10H3 (12) stereo- and regioselectively in high yields. A mechan ism is proposed to account for the observed catalytic reactions.