REMOTE SUBSTITUENT EFFECT ON THE ELECTROPHILIC ADDITIONS OF 1,3-DIENES - SYNTHESIS OF 1,2,3,4-TETRAHYDRO-10-METHOXYNAPHTHACENE-2,12-DIYL DIACETATE

The addition of one equivalent of 2-nitrobenzenesulfenyl chloride to m ethyl)-2,3,5,6-tetramethylidene-7-oxabicyclo[2.2. 1]heptane (4) is hig hly regioselective giving oromethyl)-1-(dimethoxymethyl)-5,6-dimethyli dene-3 rophenylthio)methyl]-7-oxabicyclo[2.2.1]hept-2-ene (9). The rea ction of 2-nitrobenzene-sulfenyl chloride with ene-11-oxatricyclo[6.2. 1.0(2,7)]undec-2(7)-en-4-yl methyl ketone derivatives (5, (-)-6) was a lso regioselective giving mixtures of 1,2- rather than 1,4-adducts res ulting from competitive Markovnikov and anti-Markovnikov modes of addi tion, the olefinic moiety the furthest from the 8-dimethoxymethyl subs tituent being preferred. These adducts underwent base-induced eliminat ions with the formation of exocyclic thio- and chlorosubstituted diene s that added to 2,3-didehydroanisole to give products resulting from h ighly ''ortho'' regioselective Diels-Alder additions. The regioselecti vity was the same whether 2,3-didehydroanisole was generated by nitros ation of 3-methoxy- or 6-methoxy-2-aminobenzoic acid. By applying thes e regioselective reactions to the Diels-Alder monoadduct of 3'-oxobut- 2'-en-2'-yl 5S,7S)-3-ethyl-2-oxo-3-aza-6,8-dioxabicyclo[3.2.1] octane- 7-carboxylate (1-acetylvinyl RADO(Et)) with 2,3,5,6-tetramethylidene-7 -oxabicylo[2.2.1]heptane (4), enantiopure -1,2,3,4-tetrahydro-10-metho xynaphthacene-2,5-diyl diacetate and -1,2,3,4-tetrahydro-10-methoxynap hthacen-2,12-diyl diacetate were prepared.