Cationic Rhodium(I)/Segphos-Catalyzed Cycloisomerization of 1,6- and 1,7-Diynes in the Presence of 1,2-Cyclohexanedione

Abstract

We have developed the first catalytic cycloisomerization of 1,6- and 1,7-diynes leading to trienes and vinylpyrroles by using a cationic rhodium(I)/Segphos complex (2.5-10 mol %) and 1,2-cyclohexanedione (100 mol %). 1,2-Cyclohexanedione may effectively occupy vacant coordination sites and thus promote the present cycloisomerization.

Rhodium‐Catalyzed Intramolecular Cyclization of Naphthol‐ or Phenol‐Linked 1,6‐Enynes Through the Cleavage and Formation of sp2 CO Bonds

“…The 1,6-enyne 1 reacts with rhodium to generate rhodacyclopentene A. [21] Subsequent b-hydride elimination of the propargylic hydrogen affords rhodium hydride B. Reductive elimination followed by double bond isomerization [22] affords naphthofuran 3. Alternatively, a b-oxygen elimination from rhodacyclopentene A, followed by aryl-alkenyl single bond rotation Yield[%] [b] (2 a/3 a) [ [e] PtCl 2 (CH 2 Cl) 2 80 8C, 16 h 100 0 13 [e] AuCl(PPh 3 )/AgBF 4 (CH 2 Cl) 2 80 8C, 16 h 100 0 14 [e] Pd(PPh 3 ) 4 tion of rhodium leads to allenyl phenol G, followed by 6-endo cyclization to afford benzopyran 4.…”

Rhodium‐Catalyzed Intramolecular Cyclization of Naphthol‐ or Phenol‐Linked 1,6‐Enynes Through the Cleavage and Formation of sp2 CO Bonds

“…Subsequent β‐hydride elimination of the propargylic hydrogen affords rhodium hydride B . Reductive elimination followed by double bond isomerization22 affords naphthofuran 3 . Alternatively, a β‐oxygen elimination from rhodacyclopentene A , followed by aryl–alkenyl single bond rotation in zwitterionic intermediate C and cyclization of rhodium carbene D affords oxarhodacycle E , whereupon reductive elimination of rhodium affords benzofuran 2 .…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…A subsequent β-hydride elimination followed by tautomerization in 3-25 yields pyrrole 3-23 (Scheme 180). 300 …”