Preparation of 1,3-dienyl organotrifluoroborates and their Diels–Alder/cross-coupling reactions

Boron‐ and Silicon‐Substituted [3]‐1‐Heterodendralenes as Versatile Building Blocks for the Rapid Construction of Polycyclic Architectures

“…Gratefully, this drawback can be circumvented by using a modification of the order of the reactions and by converting the initial boronic ester group in a trifluoroborate substituent that greatly increases the reactivity of the dienyl moiety. [26] This transformation was easily achieved by treatment of 9 with KHF 2 in MeOH/H 2 O with a concomitant deprotection of the alcohol. The resulting diene 27, which could be isolated if necessary, [27] was directly engaged in a Diels-Alder cycloaddition with N-phenylmaleimide at 50 8C in acetone for 12 h in the presence of various aldehydes.…”

An unusual oligomerization/oxidation reaction of a 3-boron-substituted 1-phenylbuta-1,3-diene produces 6,9,16,19-tetraphenyl-5,15-distyryl-3,13,25,26-tetraoxa-2,12-diborapentacyclo[16.2.2.28,11.12,5.112,15]hexacosa-1(20),7,10,17-tetraene

“…Complex (I) (3-BF 3 -1-Phenyl-1,3-butadiene) was prepared as described previously (De, Day, and Welker, 2007). Crystals of II were grown by evaporation of an ethyl acetate/acetone solution of (I) at 298 provided by a fine-focus sealed x-ray tube operated at 50kV and 30mA.…”

“…Most recently, we reported the preparation of several halogen substituted phenylbutadienes and their conversion into boron substituted dienes (De, Day, and Welker, 2007). To our surprise, when we attempted to grow crystals of BF 3 substituted diene (I) in ethyl acetate under atmospheric conditions we isolated a symmetrical structure (II) derived from 6 molecules of (I).…”

Rhodium catalyzed tandem Diels-Alder/hydrolysis reactions of 2-boron-substituted 1,3-dienes

“…[3] We have now subsequently reported the preparation of 2-BF 3 substituted 1,3-butadiene 1 and demonstrated that it can be used in sequential Diels-Alder/cross coupling reactions. [8,9] Given the Miyaura [10] and Hayashi [11] group's published results in rhodium catalyzed 1,4-additions of organoboron species, we wondered if boron substituted dienes could be used in a somewhat related rhodium catalyzed Diels-Alder/hydrolysis sequence (Scheme 1). With all of our experience in cobalt dienyl chemistry referenced above [3][4][5], we hoped that many of the reaction characteristics which we had discovered for cobalt dienyl chemistry (rapid Diels-Alder rates, exo selectivity, enantioselectivity with chiral metal dienes) would hold true if we could prepare related rhodium dienyl complexes 2.…”