Ortho-Selective Direct Cross-Coupling Reaction of 2-Aryloxazolines and 2-Arylimidazolines with Aryl and Alkenyl Halides Catalyzed by Ruthenium Complexes

Abstract

The ortho position of the aromatic ring in 2-aryloxazolines and 2-arylimidazolines is selectively arylated and alkenylated with organic halides in the presence of a ruthenium(II)-phosphine complex. In the case of unsubstituted and para-substituted phenyloxazolines, 1:2 coupled products were obtained preferentially, while 1:1 coupled products were obtained in the case of meta-substituted phenyloxazolines and N-acylarylimidazolines. The reaction is proposed to proceed via the generation of an organoruthenium intermediate, formed by oxidative addition of the organic halide, and ortho-ruthenation directed by the coordination of the 2-oxazolinyl or 2-imidazolinyl group to the ruthenium center.

Transition metals in organic synthesis: Highlights for the year 2005

“…Ruthenium catalyzed chelation assisted ortho-arylations of (2-pyridyl)arenes and acetophenone imines with aryl chlorides [378]. Related ruthenium-catalyzed ortho-arylations and -alkenylation of 2-aryloxazolines and 2-arylimidazolines were described [379]. Regioselective chelation-directed alkylation of sp 3 -carbon-hydrogen bonds of 2-alkylpyridines with aryl iodides was reported (Eq.…”

Rhodium-catalyzed regioselective arylation of phenylazoles and related compounds with arylboron reagents via C–H bond cleavage

“…In the case of 7, the reaction took place efficiently without adding KF. It is cited that related mono-and diarylation reactions of these substrates with aryl halides or tosylates have been reported [20][21][22][23].…”

Development of Divergent Synthetic Methods of Pyrimidobenzothiazine and Related Tricyclic Heterocycles

“…In general, C-H functionalization proceeds via metallacycle formation by oxidative addition of transition-metal and subsequent coordination of nucleophile and reductive elimination. Recent research has revealed that nitrogen-containing functional groups such as pyridines [14][15][16], imines [17][18][19], oxazolines [20,21], and amidines [22] effectively act as directing groups for regioselective C-H functionalization.…”

“…Inoue and co-workers have reported ortho-selective arylation of 2-arylimidazolines with aryl halides in the presence of a Ru(II)-phosphine complex [22] 5 For a review on Cu-mediated C-H functionalization, see [23]. 8 2 Development of Divergent Synthetic Methods of Pyrimidobenzothiazine 2-phenylimidazoline 13 with 1.2 equiv of bromobenzene using [RuCl 2 (g 6 -C 6 H 6 )] 2 yielded the mono-and diarylated products (14 and 15) in a 64 % yield and in 31:69 ratio (eq 1).…”