Andrew

Hydrogenation (see electrophilic addition) Homogeneous Catalysis The term ‘homogeneous catalysis’ refers to a catalyst that is present in the same medium as the reaction mixture – i.e. in solution. Most often used as catalysts for this are complexes of 2nd and 3rd row transition metals e.g. Rh, Ir, Pt etc. – a good example of such a complex is the much used Wilkinson’s … Read more

Full reduction with LiAlH4: All the way through to amine Partial reduction with LiAlH(OEt)3: Through to aldehyde

Esters with LiAlH4 LiAlH4 is reactive enough to reduce first to aldehyde and then through to alcohol – not able to stop at the aldehyde unless strictly one equivalent is added at low temperature (-780C). with DIBAL-H (Di-Iso-Butyl-Aluminium-Hydride) This reagent is useful because it will reduce an ester to the aldehyde and go no further; Carboxylic Acids These are difficult … Read more

Probably the most common type of reagent used for reductions in organic chemistry is the hydride reagent – i.e. one which reacts as ‘H–‘ – a hydride nucleophile. It is worth noting, however, that simple hydrides e.g. NaH are not very nucleophilic and are far more likely to act as bases. Therefore the reagentsmost likely to be encountered here are of … Read more

Oxidising Phenols with Transition Metals Note as in the Manganese Dioxide mechanism (page 1), half-hook arrows are used to represent the movements of single electrons. Oxidising Pyridine with Transition Metals

Allylic Oxidation The first step is a pericyclic ‘ene’ reaction. Diketone from ketone ‘Ene’ reaction involved again – this time in the second step.

These are oxidation reactions which also involve the cleavage of carbon-carbon bonds, with the oxidation occurring at both ends. Some will involve complete separation of 2 oxidised fragments and others will leave them connected together. Cleavage of Single Bonds i. 1,2-diols with Lead Tetra-acetate This reaction can also be carried out with NaIO4 instead of Pb(OAc)4. ii. Ketones … Read more

It is not the aim of this section to catalogue all means of oxidation for every compound imaginable, as this would be a mammoth task for both reader and writer (!), and furthermore quite unnecessary. The oxidations included here are the more commonly encountered reagents and functional groups, but should provide a general understanding of the processes involved in oxidation. To work from … Read more

Claisen A [3,3]-sigmatropic rearrangement (see Pericyclics). The driving force for the reaction is formation of the strong C=O bond Cope – similar to Claisen Also a [3,3]-sigmatropic rearrangement. The driving force in this case is opening of the strained four membered ring.

A rearrangement is an intramolecular reaction – i.e. a single molecule reacting with no external input. The topic of rearrangements is extremely nebulous and hence very difficult to cover systematically. Therefore the best approach is to look through the following few pages of (mostly) well-known rearrangements and try to deduce your own patterns and similarities. The theme … Read more