Diels-Alder reactions of dienynes

Alkynes are poor dienophiles in the Diels- Alder reaction decomposition occurs by an attempted thermal intramolecular Diels-Alder reaction of dienynes at 160 °C. In contrast, the Ni-catalysed [4+2] cycloaddition of the dienyne 50 proceeded smoothly at room temperature using tri(hexafluoro)isopropyl phosphite to give 51, which was converted to the yohimbine skeleton 52 [15]. The same reaction is catalysed by RhCl(Ph3P)3 in trifluoroethanol [16]. Intramolecular Diels-Alder reactions of the 6,8-dieneyne 53 and the 1,3,8-triene 55, efficiently catalysed by [Rh(dppe)(CH2CH2)2]SbF6 at room temperature, gave 54 and 56 [17],... 

Intramolecular homo Diels-Alder reaction of dienynes. Norbornadicnes bearing... 

Intramolecular homo Diels-Alder reaction of dienynes. Norbomadienes bearing a tethered alkyne group at C2 undergo an intramolecular homo Diels-Alder reaction when treated with 8 mol% of Co(acac)2, (C2H5)2A1CI (4 equiv.), and dppe at 25°. This reaction is particularly facile when a 5- or 6-membered ring is formed. No reaction is observed on thermal treatment of 1 at 140-170°. 

The thermal Diels—Alder reaction of dienynes (71) produced naphthalene derivatives (72) in the absence of Lewis acids, transition metals, or oxidants. The presence of the silyl group attached to the alkyne is essential for the dehydrogenation reaction to proceed (Scheme 22). The thermal intramolecular Diels—Alder reactions of (l , 7 )-l-iiitro-deca-l,7,9-trienes (73) produced trans-iused decalin cycloadducts (74) (Scheme 23). °... 

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See also in sourсe #XX -- [ ]

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