Heterobimetallic Pd–Sn Catalysis: A Suzuki, Tandem Ring-Closing Sequence toward Indeno[2,1-b]thiophenes and Indeno[2,1-b]indoles

Abstract

Indeno[2,1-b]thiophene and indeno[1,2-b]indole motifs have been obtained in moderate to good yields from easily available substituted boronic acids, 2-bromo aryl/vinyl aldehydes, and nucleophiles such as arenes/heteroarenes and others using a catalytic combination of bimetallic "Pd-Sn" and AgPF(6). This formal three-component coupling involves a Suzuki reaction followed by nucleophile assisted tandem ring closure. The sequential synthesis of substituted heterocycle-fused indenes, benzofluorene, and fluorenes was also accomplished.

Intramolecularly Stabilised Group 10 Metal Stannyl and Stannylene Complexes: Multi‐pathway Synthesis and Observation of Platinum‐to‐Tin Alkyl Transfer

“…However, the PdSn bond lengths in 3 a and 3 b are close to those in neutral Pd stannylene complexes [PdCl{2‐(Me 2 NCH 2 C 6 H 4 )}{SnCl(2,6‐(Me 2 CH 2 ) 2 C 6 H 3 )}] (2.4956(8) Å)42 and [Pd{Sn(CH(SiMe 3 ) 2 ) 2 }( i Pr 2 PC 2 H 4 P i Pr 2 )] (2.481(2) Å)43 while the PdSn bond in 4 c is closer to that in [Pd(PPh 3 ){(1‐methyl‐2‐mercaptoimidazole) 2 (SnCl 2 )}] (2.5382(1) Å) 28c. The PdSn bond in 2′d is significantly longer and approaches that of the trichlorostannyl species cis ‐[PdCl(SnCl 3 )(PPh 3 ) 2 ] (2.5760(7) Å) 44…”

“…[28c] The PdÀSn bond in 2'd is significantly longer and approaches that of the trichlorostannyl species cis-[PdCl(SnCl 3 )(PPh 3 ) 2 ] (2.5760 (7) ). [44] Concerning the electronic structure of these cationic bimetallic MÀSn species, assigning the oxidation state of the tin and Group 10 atom is not unambiguous as the bonding mode can be described by several resonance structures: [28,29] By referring to our complexes as "stannylenes", we do not intend to favour either of these hypothetical extremes. Rather we want to simply discriminate between species carrying a SnCl 2 or a SnClR unit versus those that carry a stannyl group (SnCl 3 or SnCl 2 R).…”

Ruthenium‐Catalyzed Cascade CH Functionalization of Phenylacetophenones

“…The dihydroindeno benzofuran 10 was prepared in an analogous fashion from 6 t through demethylation and acid-mediated condensation. Fused dihydroindeno heterocycles have been widely studied for their biological activity, [11] as well as applications in organic electronics [12] and organometallic chemistry (ligands for polymerization catalysts). [13] We then turned our attention to the tetracycle compound series 7.…”

Ruthenium‐Catalyzed Cascade CH Functionalization of Phenylacetophenones

“…The dihydroindeno benzofuran 10 was prepared in an analogous fashion from 6 t through demethylation and acid‐mediated condensation. Fused dihydroindeno heterocycles have been widely studied for their biological activity,11 as well as applications in organic electronics12 and organometallic chemistry (ligands for polymerization catalysts) 13…”