Medium- and Large-ring Compounds

Griesbeck et al. successfully transformed w-phthalimidoalkanoates via PET with concomitant decarboxylation and C,C combination leading to medium- and large-ring compounds with yields in the range 60-80%. Thereby, the solvent system acetone/water and K2CO3 employed for the deprotonation of the carboxylic acids were crucial (Scheme 45) [66]. 

This interesting reaction is especially useful for the synthesis of medium- and large-ring compounds from dicarboxylic esters, and is effective for ring sizes that cannot be made by the Dieckmann condensation or decarboxylation (Section 18-1 OB). Radical anions formed by addition of sodium to the ester... 

Griesbeck, A.G., Henz, A., Kramer, W., Lex, J., Nerowski, F., and Oelgemoller, M. (1997) Synthesis of medium- and large-ring compounds initiated by photochemical decarboxylation of W-phthalimidoalkanoates. Helvetica Chimica Acta, 80, 912-933. 

In the course of studying these reaction principles, the chemistry of medium and large ring compounds was investigated. This led to the discovery of the transannular reactions [5] which are a fascinating part of chemistry even today. 

Ketene, dichloroketene, and related compounds react with allylic ethers, sulfides, and selenides in a [3.3] sigmatropic rearrangement. This interesting reaction allows the synthesis of a number of medium and large ring compounds by expansion [72] [73] [74]. Dichloroketene has been prepared in situ by slow addi-... 

Ma, S. and Negishi, E.-i. (1995) PaUadium-catal3raedcyclizationof-haloallenes. A new general route to common, medium, and large ring compounds via cyclic carbopalladation. J. Am. Chem. Soc., 117, 6345-57. 

For previous reports of tandem Heck reaction-anionic capture sequences, see (a) Grigg, R., Sridharan, V. and Xu, L.-H. (1995) Palladium-catalyzed cyclization-amination of allenes - effect of base on regioselectivity of formation of allylic amines. J. Chem. Soc., Chem. Commun., 1903 and references cited therein (b) Ma, S. and Negishi, E. (1995) Palladium-catalyzed cyclization of general route to common, medium, and large ring compounds via cyclic carbopaUadation. J. Am. Chem. Soc., 117, 6345-7 and references cited therein. 

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