An easy synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerizationof readily available 2-alkynylbenzyl alcohols under neutral conditions is reported. Reactions were carried out at 70–1008Cin the presence of catalytic amounts (1–2%) of PdI2 in conjunction with 2 equiv. of KI for 1.5–24 h. The preference towards the 5-exo-digcyclization mode (leading to 1,3-dihydroisobenzofurans) or the 6-endo-dig cyclization mode (leading to isochromenes) turned out to bedependent on the substitution pattern of the substrate as well as reaction conditions. In several cases, by properly adjusting the reactionconditions, the same substrate could be selectively converted into either the dihydroisobenzofuran or the 1H-isochromene derivative.q 2003 Elsevier Ltd. All rights reserved
Versatile synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerization of 2-alkynylbenzyl alcohols
Gabriele B.
;Fazio A.;
2003-01-01
Abstract
An easy synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerizationof readily available 2-alkynylbenzyl alcohols under neutral conditions is reported. Reactions were carried out at 70–1008Cin the presence of catalytic amounts (1–2%) of PdI2 in conjunction with 2 equiv. of KI for 1.5–24 h. The preference towards the 5-exo-digcyclization mode (leading to 1,3-dihydroisobenzofurans) or the 6-endo-dig cyclization mode (leading to isochromenes) turned out to bedependent on the substitution pattern of the substrate as well as reaction conditions. In several cases, by properly adjusting the reactionconditions, the same substrate could be selectively converted into either the dihydroisobenzofuran or the 1H-isochromene derivative.q 2003 Elsevier Ltd. All rights reservedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
