Naphthalene, 2- synthesis

This naphthalene synthesis has several attractive features. The intermediate or-ganometallics need not be isolated it is regiospecific and aliphatic, aromatic, or heterocyclic acyl groups can be introduced efficiently. 

The mechanism of Wolff-Kishner reductions is exemplified in Figure 17.67 with the second step A — E of the Haworth naphthalene synthesis (steps 1 and 3 of this synthesis Fig-... 

Barth, T., Krieger, C., Neugebauer, RA. and Staab, H.A. (1991) 1,4,5,8-Tetrakis(dimethyla-mino)naphthalene synthesis, structure, proton sponge and electron donor properties. Ange-wandte Chemie — International Edition, 30, 1028-1030. 

This naphthalene synthesis proceeds in somewhat higher yields when the phthalide sulfone 4 is used in place of 1. In this reaction, 1,4-dihydroxynaph-thalenes (5) are obtained. These products can be converted into naphthoquinones or into the more stable dimethyl ethers. 

Since in the intermolecular case by the C,H activation and in the case ofthe synthesis of the fi-substituted naphthalene 30 no second five-membered ring is generated, naphthalenes are accessible by the ring expansion of the five-membered ring that is formed in the initial cyclization step. The catalytic cycle for the naphthalene synthesis is shown in Scheme 4.17. Very important is the proof of the intramolecular H-shift in the step from AB to AC by deuterium labeling studies. The ring expansion would proceed from the carbenoid species AC. 

Scheme 26.15 shows examples of naphthalene synthesis using an RCM/ elimination sequence reported by Huang and Wang [22], After ring closing of dienes 51, dehydration of the resulting RCM products 52 with silica gel gave naphthalenes... 

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