ジエン伝達Diels-Alder反応および関連反応

抄録

A new process of multiple sequence of the Diels-Alder reaction, referred to as “diene-transmissive Diels-Alder reaction”, of cross-conjugated trienes, and a stepwise sequence of double Diels-Alder reaction of cross-conjugated triene equivalents are presented. Bis (silyoxy) cross-conjugated trienes, 1 and 2, undergo two sequential Diels-Alder reactions with a variety of dienophiles giving hydronaphthalene rings. Some characteristics of this reaction have been discussed in terms of stereo-, regio-, and chemoselectivity.
Next, cross type of diene-transmissive Diels-Alder reaction has been demonstrated by using trienes, 1 and 2. The first cycloaddition stage of cross reaction, which has to be highly selective in the formation of mono-cycloadducts, has been performed by the reaction of active triene 2 with cyclic olefins or both the trienes, 1 and 2, with acyclic olefins. The second cycloadditions with a variety of dienophiles afforded cross type of bis-adducts. In the similar reactions of 2-ethoxy substituted 34 and 1-methyl substituted cross-conjugated triene 36, the initial cycloaddition selectively occurs across mono-substituted diene part in 34 and disubstituted one in 36, respectively.
Finally, cross types of stepwise sequential Diels-Alder reactions in a one-pot procedure are presented using the triene equivalents, 33, 35, 55, and 63. Among them, diene-alcohols, 55 and 63, are very useful triene equivalents, as they are readily available from the Grignard reaction of chloroprene. It is particularly noteworthy that the sequential Diels-Alder reaction using 63 provides a new method for the two six-membered rings annelation to cyclic ketones : Naphtho-annelated cycloalkanes with a variety of unsaturation are obtained by choosing the kind of dienophiles, the order of their use, and dehydrogenation.