Exotic and highly reducing neutral organic π-systems

Since the advent of the first 'super electron donors', the challenge has been to design molecules with reducing potentials tailored to discrete but difficult transformations. We now report the synthesis of compound II, the most reducing neutral organic compound yet announced, with a reduct...

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Bibliographic Details
Main Author: Farwaha, Hardeep S.
Published: University of Strathclyde 2012
Subjects:
540
Online Access:http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576392
Description
Summary:Since the advent of the first 'super electron donors', the challenge has been to design molecules with reducing potentials tailored to discrete but difficult transformations. We now report the synthesis of compound II, the most reducing neutral organic compound yet announced, with a reduction potential of -1.46 V vs. Ag/AgCl. This new electron donor reduces Weinreb amide III and sulfonamide V and VII more efficiently than any previously synthesised organic electron donor. Further showcasing its reactivity, donor compound II is also able to carry out Birch reduction of anthracene derivative compound IX in satisfactory yield at room temperature. Compound II is the prototype for 3rd generation organic donors and raises the question of what limits exist in the design of neutral organic electron donors. With this initial success, extended donor XI was also synthesised and studied. The spectroscopic and electrochemical data for this exotic donor species were found to be very perplexing and its properties are discussed in detail. A range of 'donor precursor' compounds (XII-XVII) were also synthesized for applications in electrocatalysis and for further development of super electron donors with unprecedented reactivity. The trapping of radical-anion intermediates XVIII and XX arising from metal-free Birch reduction of cyclopropanes was also explored. For this purpose, the synthesis of cyclopropane test substrates XXII and XXIV was achieved and their reactivity with UV-activated 4-DMAP-derived donor XXVI was studied. The results from this work show that isomerisation occurs through ring-opening and ring-closing of the cyclopropane ring and that products arising from 5-exo-cyclisation of the Birch intermediates do not form.