cyclopentadiene (12) were investigated in aqueous medium, in organic solvent and under solventless conditions. The reactions performed in water occurred in heterogeneous phase but were faster than those executed in toluene or dichloroethane (DCE). 1a-c, 5, and 6 behaved as 2pi components in the Diels-Alder cycloadditions with 7-10 and 12, and exo adducts were preferentially or exclusively produced. Surprisingly
                                    3-硝基
香豆素(1a),6-
氯-
3-硝基
香豆素(1b)和6-,7-和8-羟基-
3-硝基
香豆素(1c,5和6)的[4 + 2]环加成(E)-
戊二烯(7),
异戊二烯(8),
2,3-二甲基-1,3-丁二烯(9),
2-甲氧基-1,3-丁二烯(10),
2,3-二甲氧基-1,在
水性介质中,有机溶剂中和无溶剂条件下研究了3-
丁二烯(11)和
环戊二烯(12)。在
水中进行的反应发生在异相中,但比在
甲苯或
二氯乙烷(DCE)中进行的反应要快。在Diels-Alder环加成7-10和12中,1a-c,5和6表现为2pi成分,并且优先或专门生产exo加成物。出乎意料的是,1a在
水中的环加成中表现为4pi成分,分离出11和4-取代的3-
硝基苯并二氢
吡喃酮20和21。羟基-
3-硝基
香豆素1c,5和6与1,3-二烯9的环加成反应在
水或有机溶剂中不起作用,但在无溶剂条件下起作用。源自正常电子需求Diels-Alder反应的