Domino Heck-Diels-Alder reaction

Scheme 27. Domino Heck-Diels-Alder reaction and formation of dendralenes by cycloisomerization of enediynes...

Knoke and de Meijere [60] recently developed a highly flexible domino Heck-Diels-Alder reaction of a symmetrically substituted cumulene 125, which also involves cross-couplings of an allene at the central position. Both aryl and hetaryl halides react efficiently with l,3-dicyclopropyl-l,2-propadiene (125) and furnish 1,3,5-hexatriene derivatives 126 as intermediates, which are usually trapped by acceptor-substituted olefins in a subsequent cycloaddition, providing adducts 127a/b in moderate to good overall yields (Scheme 14.30). 

Scheme 16.28 Domino Heck—Diels—Alder reaction.

Schemes . Domino Heck-Diels-Alder reactions of bicyclopropylidene (1) [147,148]...

Methyl 2-bromo-2-cyclopropylideneacetate (11a) has never been tested in these reactions, but has been used as a starting material for the stepwise construction of 1,6-heptadienes with methylenecyclopropane units for intramolecular Heck reactions. Thus, bromo ester 11a, after reduction, subsequent conversion of the resulting alcohol to the bromide and coupling with enolates of substituted malonates, was transformed into dienes of the type 254 (Scheme 73) - versatile synthetic blocks for the preparation of functionally substituted spirocyclopropanated bicyclo[4.3.0]nonenes 255a-d by a domino Heck-Diels-Alder reaction [122a]. 

Scheme 2 Early examples of domino Heck-Diels-Alder reactions [19]...

Starting from suitably substituted 2-bromotrideca-l,ll-diene-6-ynes, an all-intramolecular domino Heck-Diels-Alder reaction can occur which features the formation of even four rings. When (E/Z)-125 is treated with... 

This is a general procedure for a domino Heck/Diels-Alder reaction [69] (Scheme 3-58). To a solution of diethyl allyl(2-bromoallyl)malonate (261) [257] (640 mg, 2.01 mmol) in acetonitrile (16 mL) in a screw-capped Pyrex bottle were added Pd(OAc)2 (14 mg, 3 mol%), PPh3 (42 mg, 8mol%), silver carbonate (665 mg, 2.41 mmol), and methyl 2-chloro-2-... 

Another potentially powerfnl sequence arises by combining one or two intramolecular Heck-type couplings with an intra- or intermolecular Diels-Alder addition (for early examples of inter-intermolecular one-pot domino Heck-Diels-Alder reactions see Refs. [49] and [50]). An all-intramolecular version of such a sequence has been shown to proceed reasonably smoothly for terminally alkoxycarbonyl-substituted 2-bromotrideca-l,ll-dien-6-ynes under palladium catalysis at 130 °C. At 80 °C, the sequential reaction stops after the two consecutive Heck-type cyclizations and subsequent /3-hydride elimination to give a 1,3,6-triene apparently only the ( )-isomer undergoes the intramolecular Diels-Alder reaction, as the (Z)-l,3,6-triene is observed accompanying the tetracyclic system obtained at 130 °C (Scheme 36). 

How Ang, K., Brase, S., Steinig, A.G., et al. (1996) Versatile synthesis of bicyclo[4.3.0]nonenes and bicyclo[4.4.0]decenes by a domino Heck-Diels-Alder reaction. Tetrahedron, 52,11503-28. 

Korbe, S., de Meijere, A. and Labahn, T. (2002) Construction of bi- and tricyclic skeletons by domino-Heck-Diels-Alder reactions. Helv. Chim. Acta, 85, 3161-75. 

Knoke, M. and de Meijere, A. (2003) A versatile access to l-cyclopropyl-2-aryl-1,3,5-hexatrienes - domino Heck-Diels-Alder reactions of l,3-dicyclopropyl-l,2-propadiene. Synlett, 195-8. 

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