Diradical-promoted (n + 2 - 1) ring expansion: An efficient reaction for the synthesis of macrocyclic ketones
(Chemical Equation Presented) A diradical-promoted (n + 2 - 1) ring expansion reaction based on vinyl side chain insertion (+2C) and decarbonylation (-1C) has been developed. Flash vacuum pyrolysis (FVP) of medium- and large-ring 2-trimethylsilyloxy-2-vinyl-cycloalkanones at 500-600°C affords the one-carbon ring-expanded cycloalkanones in good yields. Methyl groups on the vinyl moiety are transformed regiospecifically as corresponding α- and β-substituents, respectively. 2-Ethynyl precursor analogues react in a manner similar to give α,β-unsaturated cyclic ketones.
Short and versatile two-carbon ring expansion reactions by thermo-isomerization: Novel straightforward synthesis of (±)-muscone, nor- and homomuscones, and further macrocyclic ketones
Thermo-isomerization of 1-vinyl substituted medium-and large-ring cycloalkanol derivatives in a flow reactor system at temperatures of 600°C to about 650°C leads directly to the ring-expanded macrocyclic ketones. Alkyl substituents at the vinylic moiety are transferred locospecifically to the ring-expanded ketone as corresponding α-, and β-substituents, respectively. This novel thermal 1,3-C shift reaction therefore provides a new access to short syntheses of many alkyl-substituted macrocyclic ketone derivatives [e.g. (±)-muscone and analogues] in a systematic manner.
Nagel, Matthias,Hansen, Hans-Jürgen,Fráter, Georg
p. 280 - 284
(2007/10/03)
Macrocyclic ring closure of OH-assisted Prins reaction. A new and efficient synthesis of (R, S)-muscone
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Schulte-Elte,Hauser,Ohloff
p. 2673 - 2680
(2007/10/10)
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