The Beginnings of Thio urea Catalysis

1) as always in catalysis, if the catalyst can interact with the starting material, the transition state (TS), and the products, it is necessary that the relative stabihza-tion of the TS is the largest this can be probed by computational methods  

2) the bi- or multidentate mode of catalyst-substrate binding increases catalytic efficiency and restricts degrees of freedom  

4) to avoid self-association the catalyst should not incorporate strong hydrogen bond acceptors such as ester or nitro groups the non-coordinating acidifying CF3 group as in the 3,5-(trifluoromethyl)phenyl moiety is an excellent choice in this respect [17]  

5) weak enthalpic interactions reduce product inhibition, allowing substoichio-metric amounts of the catalyst  

6) the catalyst should ideally be water compatible or even catalyticaUy active in water[lb, Ig]. 

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