14595-54-1Relevant academic research and scientific papers
Diradical-promoted two-carbon ring-expansion reactions by thermal isomerization: Synthesis of functionalized macrocyclic ketones
Rueedi, Georg,Hansen, Hans-Juergen
, p. 1628 - 1665 (2007/10/03)
A new method for the smooth and highly efficient preparation of functionalized macrocyclic ketones has been developed. Pyrolysis of medium- and large-ring 3-vinylcycloalkanones by dynamic gas-phase thermo-isomerization (DGPTI) at 600-630° yielded, under insertion of a previously attached vinyl side chain by means of a 1,3-C shift, the corresponding γ,δ- unsaturated cycloalkanones. The yield of the two-carbon ring-expanded ketones greatly depended on the relative ring strains of substrate and product (5-87%, cf. Table 5). The formation of minor amounts of one-carbon ring-expanded cycloalkenes (10%) can be ascribed to a subsequent decarbonylation step. A reaction mechanism involving initial cleavage of the weakest single bond in the molecule has been established (cf. Scheme 6). Recombination within the generated diradical intermediate in terminal vinylogous position led to the observed products, while reclosure gave recovered starting material. Substituents on the vinyl moiety were transferred locospecifically into the ring-expanded products. An isopropenyl group did not significantly affect the isomerization process, whereas substrates bearing a prop-1-enyl group in β-position enabled competing intramolecular H-abstraction reactions, leading to acyclic dienones (cf. Schemes 9-11). DGPTI of the 13-membered analogue directly yielded 4-muscenone, which, upon hydrogenation, led to the valuable musk odorant (±)-muscone. Increasing the steric hindrance on the vinyl moiety gave rise to diminishing amounts of the desired γ,δ-unsaturated cycloalkanones. This novel two-carbon ring-expansion protocol was also successfully applied to 3-ethynylcycloalkanones, giving rise to the corresponding ring-expanded cyclic allenes (cf. Scheme 13).
A Novel and Highly Efficient Two-Carbon Ring Expansion
Rueedi, Georg,Nagel, Matthias,Hansen, Hans-Juergen
, p. 4211 - 4213 (2007/10/03)
(Equation presented) Dynamic gas-phase thermoisomerization (DGPTI) of medium- and large-ring 3-vinylcycloalkanones at 600-630°C produces isomeric γ,δ-unsaturated cycloalkanones expanded by two carbon atoms. A reaction mechanism involving an open-chain diradical intermediate, followed by intramolecular recombination under insertion of the vinyl group is proposed. Substituents on the vinyl moiety are transferred locospecifically to the ring-expanded ketones as corresponding β- and γ-substituents, respectively. The preparation of extraordinary cyclic allenes can be accomplished by DGPTI (540°C) of 3-ethinylcyclododecanone.
Macrocyclic ketones as fragrance materials and methods for making same
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, (2008/06/13)
Novel macrocyclic diene ketone compounds useful as fragrance materials are described having the following general formula (I): where R1, R2, R3and R4are each either a hydrogen atom or a C1to C4alkyl, a is the integer 1 or 2 and b is an integer in a range from 1 to 6. Novel pathways are described for synthesizing these macrocyclic diene ketones, as well as saturated and mono-unsaturated macrocyclic ketones having the following general formula (IV): where R1, R2, R3and R4are each independently a hydrogen atom or a C1to C4alkyl, a is the integer 1 or 2 and b is an integer in a range from 1 to 6.
