Abstract
This short paper details our experiences with Pd- and Pt-catalyzed cross-coupling and cyclization reactions in investigations covering the years from 1997 until now. Pd-catalysed Suzuki-Miyaura-, Heck- and Sonogashira-type cross coupling reactions in conjunction with other transformations in one pot, especially with the Wittig reaction, are highlighted. This is followed by a description of a combination of Heck- and cyclization reactions. Finally, Pt-catalyzed diene-yne cyclization reactions are discussed.
Highlights
Our first contact with Pd-catalyzed cross-coupling reactions came when attempting to construct functionalized estradiol derivatives as potential diagnostic agents for estrogen receptor-positive breast cancer [1 - 3]
In order to have a platform to diversify the molecules that could be prepared, a synthetic sequence was developed by constructing stabilized phosphoranes with a terminal haloaryl unit on a polymer backbone stemming from triphenylphosphinepolystyrene, derivatising the phosphoranes by C-C cross-coupling reaction and reacting the phosphoranes prepared with a steroidal carbaldehyde [5]. This clearly showed that stabilized phosphoranes are compatible with reaction conditions needed to carry out many of the C-C cross-coupling reactions and would lead to the development of one-pot reactions involving Pd-catalyzed cross-coupling reactions and Wittig olefinations [6 - 8]
One of our Heck-reaction cyclization sequences came from the desire to functionalize estrane derivatives, this time at C7, by submitting a η6-estra-1,3,5(10),6-trien-17-one 17,17-acetal tricarbonylchromium(0) [9] to a Heck reaction, which led to a surprising triarylation of the compound with concurrent cyclization
Summary
Our first contact with Pd-catalyzed cross-coupling reactions came when attempting to construct functionalized estradiol derivatives as potential diagnostic agents for estrogen receptor-positive breast cancer [1 - 3] This involved Wittig olefination reactions of formylestrane derivatives with stabilized phosphoranes [4]. Open Chemistry Journal, 2018, Volume 5 77 catalyst, in the presence of PPh3 (3 equiv.). These were sufficiently active to catalyze Suzuki-Miyaura reactions with chloroarenes, where the chloro group was activated by a nitro substituent or as part of a quinoid system as in chloroanthraquinones [13] and 1-chloro-2,4-dinitrobenzene [14]. A number of experimental procedures can be found as representative examples
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