Fairlamb Research Group

Catalysis, Synthetic and Mechanistic Chemistry

Push-Pull Alkenes and Alkynes

Push-pull organic and organometallic systems exhibit interesting tuneable properties in the design of advanced materials, therapeutics, ligand and metal catalyst design. Selected examples are given below: 

Purines containing push-pull alkynes: Synthesised by Sonogashira cross-coupling reactions, 8-substituted purines (adenosines and guanosines) exhibit interesting fluorescence properties, based on their push-pull electronic effects.

Lead reference: 

Org. Biomol. Chem. 2015, 13, 68.


Aryl-alkyne-2-pyrones: The group has worked on the synthesis of push-pull aryl-alkynyl-2-pyrones.  Derivatives possess anti-cancer properties, and exhibit favourable fluorescent behaviour.

Lead reference: 

Chem. Commun. 2005, 2666-2668.


 



Pauson-Khand reactions: Using sterically comparable (2-phenylethynyl) heteroaromatic compounds PK reactions with norbornene, mediated by Co2(CO)8, to give cyclopentenone products, were examined.

The type of heteroaromatic group was shown to dramatically influence PK regioselectivity. This can be partly explained by rationalization of the current reaction mechanism but not fully.

Lead reference:

J. Org. Chem. 2011, 76, 5320-5334.



Fe(CO)3(eta-3-diene) complexes: A series of iron(0) tricarbonyl complexes containing eta-4-bound alpha,beta unsaturated enone ligands [Fe(CO)3(eta-4-RCH=CH-C{Ph}=O)] facilitated a comprehensive correlation of the electronic withdrawing/donating properties of the substituent (R) with the strength of the metal-ligand interaction. Spectroscopic analysis (IR, NMR) was key to determining the electronic effects.  A IR correlation with the Hammett parameter, sigma, is given opposite. Enone back-bonding (synergic) is most pronounced for the electron-withdrawing systems (here a shift closer to free CO is seen, indicative of less Fe-CO back-bonding as the enone ligand becomes more electron-deficient.  

Lead reference:

Organometallics 2007, 26, 6354-6365.


Aryl-substituted dibenzylidene acetones and their use in Pd-catalysed cross-coupling processes: The aryl substituent plays a remarkable role in altering the electronic properties of the 1,5-dien-3-one moiety. Ab initio calculations on the free ligands indicate that the electron density at the C=C bonds correlates well with their efficacy in general cross-coupling processes mediated by palladium. 

Lead reference:

Organometallics 2007, 26, 4087-4089.  

Calculated HOMO and LUMO for 4,4'-OMe substituted dibenzylidene acetone.


A figure showing how the electronic effects of the dba-Z ligand affects cross-coupling efficacy.




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