Several substituted cyclopropylallenes were coupled under Heck conditions with aryl iodides and aryl bromides, respectively, and the 1,3,5-hexatrienes resulting with ring-opening of the cyclopropyl group, were captured in situ by a number of reactive dienophiles to yield oligosubstituted cyclohexene derivatives (8-86 %, 33 examples) with diastereomeric ratios ranging from 1.4:1 to 4.9:1. The influences of the number, the
Cyclopropane derivatives
Cyclopropane derivatives Q 0021Cyclopropyl Building Blocks for Organic Synthesis. Part 85. A Versatile Access to 1-Cyclopropyl-2-aryl-1,3,5-hexatrienes -Domino Heck-Diels-Alder Reactions of 1,3-Dicyclopropyl-1,2-propadiene. -An efficient three-step synthesis of the allene (V) is described. It is found to undergo Pd-catalyzed domino Heck-Diels-Alder reaction with aryl halides and dienophiles via hexatriene intermediates. - (KNOKE, M.; DE MEIJERE*, A.; Synlett 2003, 2, 195-198; Inst. Org. Chem.,
Cyclohexane derivatives Q 0040 Small Ring Building Blocks for Organic Synthesis. Part 110. Domino Heck--Diels-Alder Reactions of Differently Substituted Cyclopropylallenes. -A sequential Heck and Diels-Alder reaction is a useful access to 4,5-disubstituted 3-alkenylcyclohexenes starting from easily prepared cyclopropylallenes (I) and commercially available aryl halides and dienophiles. The title compounds are obtained with yields of 8-86% (33 examples) and diastereomeric ratios ranging from 1.4:1 to 4.9:1. -(KNOKE, M.; DE MEIJERE*, A.; Eur.
An efficient three-step synthesis of 1,3-dicyclopropyl-1,2-propadiene (4) (overall yield 68%) starting from dicyclopropylacetylene was developed. The allene, when coupled with several aryl iodides and aryl bromides under palladium catalysis in the presence of a reactive dienophile, was found to undergo a domino Heck-Diels-Alder reaction to yield 3-(1′-arylalkenyl)-substituted cyclohexenes 9 in moderate to good yields (36-86%).
The Pauson-Khand-like carbonylative cocyclizations of alkynes with cyclopropylallene and with 1,3-dicyclopropylallene occur regioselectively and lead to 4-(cyclopropylmethylene)cyclopentenones (43-59% for six examples).
The reaction of allenes (II) proceeds without opening of the cyclopropyl ring providing 4-(cyclopropylmethylene)cyclopentenones in a regioselective manner. -(AHMAR, M.; KNOKE, M.; DE MEIJERE, A.; CAZES*, B.; Synthesis 2007, 3, 442-446; Lab. Chim. Org., CNRS, Univ. Claude Bernard Lyon, F-69622 Villeurbanne, Fr.; Eng.) -Mais 23-060
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