Ruthenium‐Catalyzed Synthesis of 2,3‐Cyclo[3]dendralenes and Complex Polycycles from Propargyl Alcohols

Abstract

Ruthenium-catalyzed cascade transformations for the synthesis of 2,3-cyclo[3]dendralenes and multicomponent processes based thereon to generate complex polycycles are presented. The combination of allylation-cyclization sequences with diene-transmissive Diels-Alder reactions allows the rapid and selective construction of natural-product-like motifs from easily accessible starting materials in a one-pot process and provides a new method to access potential drug candidates.

Ruthenium‐Catalyzed Cascade Annulation of Indole with Propargyl Alcohols

“…In agreement with our previously reported studies,– we assume that the initially formed π‐complex 15 is in equilibrium with the alkynyl species 16 – 18 . Alkynyl complex 16 , formed from substrate 1 , is attacked by indole and generates enynol 19 .…”

Ruthenium‐Catalyzed Cascade Annulation of Indole with Propargyl Alcohols

“…In agreement with our previously reported studies,– we assume that the initially formed π‐complex 15 is in equilibrium with the alkynyl species 16 – 18 . Alkynyl complex 16 , formed from substrate 1 , is attacked by indole and generates enynol 19 .…”

Room-Temperature Chemoselective Reductive Alkylation of Amines Catalyzed by a Well-Defined Iron(II) Complex Using Hydrogen

“…Such reactivity might be associated to the electron-richness of the cyclopentadienone. Finally, following a procedure reported by Gompper, the aminocyclopentadienylium ligand 2 was prepared in two steps from 1,4-dimethyl-5,7-diphenyl-3,4-dihydro-1 H -cyclopenta­[ b ]­pyrazin-6-(2 H )-one 1 in a 51% overall yield (steps (i) and (ii), Scheme ). A simple heating of this ligand with [Fe 2 (CO) 9 ] in toluene provided, not the expected cyclopentadienone iron(0) tricarbonyl complex Fe2 , but the cyclopentadienyl iron­(II) complex Fe3 in 49% yield, through a redox process (Scheme ).…”

Synthesis of Triaminocyclopentadienyl Iron(II) Tricarbonyl Complexes and Application to the Synthesis of Aminophosphines

“…The latter was refluxed in toluene with [Fe 2 (CO) 9 ] for 16 hours and the iron complexes Fe1‐5 were isolated in 25–32% overall yields (3 steps, Scheme 2). Fe6 bearing a NH 2 function was prepared following a procedure described by Haack for the ruthenium congener [14] . The amino function was introduced by adding an excess of formamide to the diaminocyclopentadienylium intermediate under basic conditions.…”

“…According to the procedure previously reported by Haak, [14] starting from 1,4‐dimethyl‐5,7‐diphenyl‐1,2,3,4‐tetrahydro‐6H‐cyclopenta[b]pyrazin‐6‐one (3.13 mmol, 1 equiv., 1.0 g), in the presence of triethyloxonium tetrafluoroborate (3.44 mmol, 1.1 equiv. ), formamide (12.57 mmol) and triethylamine (6.26 mmol) in dichloromethane (15 mL), the purified cationic ligand was isolated in 55% yield as blue foam.…”

Ruthenium‐Catalyzed Cascade Annulation of Indole with Propargyl Alcohols

“…In agreement with our previously reported studies,– we assume that the initially formed π‐complex 15 is in equilibrium with the alkynyl species 16 – 18 . Alkynyl complex 16 , formed from substrate 1 , is attacked by indole and generates enynol 19 .…”

Room-Temperature Chemoselective Reductive Alkylation of Amines Catalyzed by a Well-Defined Iron(II) Complex Using Hydrogen

“…Such reactivity might be associated to the electron-richness of the cyclopentadienone. Finally, following a procedure reported by Gompper, the aminocyclopentadienylium ligand 2 was prepared in two steps from 1,4-dimethyl-5,7-diphenyl-3,4-dihydro-1 H -cyclopenta­[ b ]­pyrazin-6-(2 H )-one 1 in a 51% overall yield (steps (i) and (ii), Scheme ). A simple heating of this ligand with [Fe 2 (CO) 9 ] in toluene provided, not the expected cyclopentadienone iron(0) tricarbonyl complex Fe2 , but the cyclopentadienyl iron­(II) complex Fe3 in 49% yield, through a redox process (Scheme ).…”

Synthesis of Triaminocyclopentadienyl Iron(II) Tricarbonyl Complexes and Application to the Synthesis of Aminophosphines

“…The latter was refluxed in toluene with [Fe 2 (CO) 9 ] for 16 hours and the iron complexes Fe1‐5 were isolated in 25–32% overall yields (3 steps, Scheme 2). Fe6 bearing a NH 2 function was prepared following a procedure described by Haack for the ruthenium congener [14] . The amino function was introduced by adding an excess of formamide to the diaminocyclopentadienylium intermediate under basic conditions.…”

“…According to the procedure previously reported by Haak, [14] starting from 1,4‐dimethyl‐5,7‐diphenyl‐1,2,3,4‐tetrahydro‐6H‐cyclopenta[b]pyrazin‐6‐one (3.13 mmol, 1 equiv., 1.0 g), in the presence of triethyloxonium tetrafluoroborate (3.44 mmol, 1.1 equiv. ), formamide (12.57 mmol) and triethylamine (6.26 mmol) in dichloromethane (15 mL), the purified cationic ligand was isolated in 55% yield as blue foam.…”

Ruthenium‐Catalyzed Cascade Annulation of Indole with Propargyl Alcohols

“…In agreement with our previously reported studies,– we assume that the initially formed π‐complex 15 is in equilibrium with the alkynyl species 16 – 18 . Alkynyl complex 16 , formed from substrate 1 , is attacked by indole and generates enynol 19 .…”

Room-Temperature Chemoselective Reductive Alkylation of Amines Catalyzed by a Well-Defined Iron(II) Complex Using Hydrogen

“…Such reactivity might be associated to the electron-richness of the cyclopentadienone. Finally, following a procedure reported by Gompper, the aminocyclopentadienylium ligand 2 was prepared in two steps from 1,4-dimethyl-5,7-diphenyl-3,4-dihydro-1 H -cyclopenta­[ b ]­pyrazin-6-(2 H )-one 1 in a 51% overall yield (steps (i) and (ii), Scheme ). A simple heating of this ligand with [Fe 2 (CO) 9 ] in toluene provided, not the expected cyclopentadienone iron(0) tricarbonyl complex Fe2 , but the cyclopentadienyl iron­(II) complex Fe3 in 49% yield, through a redox process (Scheme ).…”

Synthesis of Triaminocyclopentadienyl Iron(II) Tricarbonyl Complexes and Application to the Synthesis of Aminophosphines

“…The latter was refluxed in toluene with [Fe 2 (CO) 9 ] for 16 hours and the iron complexes Fe1‐5 were isolated in 25–32% overall yields (3 steps, Scheme 2). Fe6 bearing a NH 2 function was prepared following a procedure described by Haack for the ruthenium congener [14] . The amino function was introduced by adding an excess of formamide to the diaminocyclopentadienylium intermediate under basic conditions.…”

“…According to the procedure previously reported by Haak, [14] starting from 1,4‐dimethyl‐5,7‐diphenyl‐1,2,3,4‐tetrahydro‐6H‐cyclopenta[b]pyrazin‐6‐one (3.13 mmol, 1 equiv., 1.0 g), in the presence of triethyloxonium tetrafluoroborate (3.44 mmol, 1.1 equiv. ), formamide (12.57 mmol) and triethylamine (6.26 mmol) in dichloromethane (15 mL), the purified cationic ligand was isolated in 55% yield as blue foam.…”