Regioselectivity coordination theory

Also in 1986, Bose s group in India observed a reversal of regiochemistry for the Wacker oxidation of S-vinyM-substituted -azetidinones.22 For instance, vinyl-lactam 11 was converted to the corresponding aldehyde 12 exclusively in 70% yield. The authors suggested that palladium coordinated with die carbonyl of the lactams as well as the olefin double bond, which influenced the regioselectivity of the hydration step. This was the first time the heteroatom coordination theory was put forward and it has been widely adopted since then. 

Another extreme of the regioselectivity of the Wacker oxidation was found in the oxidation of olefin 93.68 As shown below, in the synthesis of ( )-B(9a)-homo-C-nor-3-methoxy-12-oxa-17-vinylestra-l,3,5(10)-trienes, olefin 93 was converted to aldehyde 94 as the sole product. The regiochemical outcome could be readily explained by the heteroatom coordination theory. 

In 1982 the present author discovered cyclic orbital interactions in acyclic conjugation, and showed that the orbital phase continuity controls acyclic systems as well as the cyclic systems [23]. The orbital phase theory has thus far expanded and is still expanding the scope of its applications. Among some typical examples are included relative stabilities of cross vs linear polyenes and conjugated diradicals in the singlet and triplet states, spin preference of diradicals, regioselectivities, conformational stabilities, acute coordination angle in metal complexes, and so on. 

The theory of regioselective synthesis of metal complexes is based on the ideas of competitive coordination and the principle of hard and soft acids and bases (HSAB, Sec. 1.2.2). 

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