Synthesis of 1,2-Disubstituted Cyclopentadienes from Alkynes Using a Catalytic Haloallylation/Cross-Coupling/Metathesis Relay

Abstract

A three-step method based on Pd-catalyzed haloallylation of alkynes, Pd-catalyzed cross-coupling, and Ru-catalyzed ring-closing metathesis constitutes a new and short approach to variety of 1,2-substituted cyclopentadienes. The scope of the method is broad with respect to different substituents (alkyl, aryl, metallocenyl, and other substituents as well as their combinations are tolerated), and all steps proceeded with sensible yields. As a demonstration of product utility, several of the prepared cyclopentadienes were converted into the corresponding ferrocenes.

Total synthesis of rupestine G and its epimers

“…After screening several Suzuki cross-coupling conditions, it was found that using isopropenylboronic acid pinacol ester, instead of unstable prop-1-en-2-ylboronic acid, gave compound 11 in 92% yield [20][21][22][23][24]. The pivotal RCM reaction catalysed by the Grubbs II catalyst was carried out to build the seven-membered ring in 53% yield [25][26][27][28]. According to the NMR data, the ring-closed product favoured the enol form 13 rather than the keto form 12, although both of the two tautomers were detectable on thin layer chromatography.…”

Synthetic Routes towards Multifunctional Cyclopentadienes

“…Rhodium‐catalyzed cross‐coupling with vinylmetals led to substituted 1,3,6‐trienes. The final Cp‐forming step was a Grubbs I promoted ring‐closing metathesis reaction . Although a series of substituents were introduced into the Cp framework, the authors reported difficulties in the purification and isolation of some final products.…”

“…The final Cp-forming step was aG rubbs Ip romoted ring-closing metathesis reaction. [18] Althoughaseries of substituents were introduced into the Cp framework, the authorsr eported difficulties in the pu-rificationa nd isolation of some final products.C ps bearing an ethyl or methyl ester functionality were found to not be stable enough for isolation. Nevertheless, most Cps were obtained in their pure form in good yields (58-83 %) and the respective ferrocened erivatives werealso prepared in one step.…”

Scope and Mechanistic Investigations of Pd-Catalyzed Coupling/Cyclization and Cycloisomerization of Allenyl Malonates

“…Highly substituted cyclopentenes and cyclopentanes are important substructures in a variety of complex natural products and pharmaceuticals (Figure ). Diverse synthetic methods have been developed to access these cores, including cycloadditions, ring-closing metatheses, Conia-ene cyclizations, and carbonyl-ene cyclizations, among others. However, these strategies differ in the ease with which stereochemical complexity can be introduced into the products.…”