Hydrogenation single aromatic rings

The greatest progress in this area has been made in the reduction of bi-cyclic heterocyclic compounds which are presumably easier to hydrogenate than single aromatic rings as aromatic stabilisation of the heteroaryl ring is lowered in bicyclic systems. For example, a variety of catalytic systems have been developed for the synthesis of quinolines as illustrated in Scheme 14.23. Quinoline 63 can be reduced under either metal-catalysed pressure or transfer hydrogenation conditions, or Bronsted acid... 

The regioselectivity of electrophilic addition is governed by the ability of an aromatic ring to stabilize an adjacent carbocation. This is clearly seen in the addition of hydrogen chloride to indene. Only a single chloride is formed. 

A fist of the metal complexes that have been claimed to generate catalysts for the hydrogenation of carbocyclic aromatic rings is provided in Table 16.1. This list includes homogeneous catalysts, biphase catalysts, and tethered single-site catalysts. 

Aryl Group an aromatic ring from which a single hydrogen has been removed Assimilate to incorporate into the body Atmosphere envelope of gas surrounding Earth s surface composed primarily of nitrogen and oxygen... 

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