Coupling of 7-methoxy-8-(3-methyl-2-butenyl)-2H-1-benzopyran  (4a) with 2-chloromercurio-4,5-methylenedioxyphenol (5) yields (±)-6a,  12a-cis-dihydro-3-methoxy-4-(3-methyl-2-butenyl)-6H-[1,3]dioxolo  [5,6]benzofuro[3,2-c][1]benzopyran (6; ±-4-prenylpterocarpin)  in an efficient manner. An improved procedure for the preparation of  chromenes is reported.
                                    7-甲氧基-8-(3-甲基-
2-丁烯基)-2H-1-苯并
吡喃(4a)与2-
氯汞-4,5-亚甲基二氧基
苯酚(5)的偶联以有效的方式产生(±)-6a,12a-顺式二氢-3-甲氧基-4-(3-甲基-
2-丁烯基)-6H-[1,3]二氧杂
环戊烯并[5,6]
苯并呋喃并[3,2-c][1]苯并
吡喃(6;±-4-异
戊烯基蝶呤)。本文报道了一种改进的苯并
吡喃制备方法。