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2-(1-Hydroxyalkyl)-1,4-naphthoquinones are found to react with pyrrolidino enamines in toluene to give 1H-naphtho[2,3-c]pyran-5,10-diones in good yields via a tandem conjugate addition-cyclization sequence, followed by an elimination of pyrrolidine. 2-Hydroxymethyl-1,4-naphthoquinone and morpholino enamines undergo a similar sequence, without loss of morpholine, to yield 3-morpholino-3,4-dihydro-1H-naphtho[2,3-c]pyran-5,10-diones. The 3-morpholino group of these products can be replaced with a hydro, a hydroxy, or a methoxy group. Imines also react with 2-(1-hydroxyalkyl)-1,4-naphthoquinones to give the corresponding 1H-naphtho[2,3-c]pyran-5,10-diones, including a natural product (pentalongin). The utility of these reactions is demonstrated in the synthesis of pyranonaphthoquinone antibiotics, viz. (±)-eleutherin and (±)-isoeleutherin.

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1-(2-Isocyanophenyl)pyrroles have been prepared. They react in moderate to good isolated yields with aldehydes (or ketones), oxiranes, and acetals in the presence of catalytic amounts of diethyl ether–boron trifluoride to give pyrrolo[1,2-a]quinoxalines carrying an oxyalkyl substituent, such as α-hydroxyalkyl, β-hydroxyalkyl, or α-alkoxyalkyl, at the 4-position.