Ruthenium‐Catalyzed C7‐Formylmethylation or Sequential Acetalization of Indolines with Vinylene Carbonate in Different Solvents

Abstract

The ruthenium‐catalyzed C7‐formylmethylation or sequential acetalization of indolines with vinylene carbonate has been realized under simple and easy‐to‐operate reaction systems. Several preliminary mechanistic studies and derivatization reactions for the conversion of formylmethyl group were also performed. This transformation offers an alternative approach for the direct conversion of C(sp2)−H to formylmethyl or corresponding acetal structure.

Rhodium(III‐Catalyzed C8‐Selective C−H Alkenylation and Alkylation of 1, 2, 3, 4‐Tetrahydroquinolines with Styrenes and Allylic Alcohols

“…Considering the remarkable performance of the readily accessible and removable N‐(2‐pyrimidyl) directing group in controlling the site selectivity and promoting the reactivity in transition‐metal catalyzed C−H functionalization of 1,2,3,4‐tetrahydroquinolines, [11k–q] we envisioned that the direct alkenylation of C8−H of 1,2,3,4‐tetrahydroquinolines may also be facilitated by such a directing group. With this in mind, we started our investigations by examining the direct alkenylation of 1‐(pyrimidin‐2‐yl)‐1,2,3,4‐tetrahydroquinoline ( 1 a ) with styrene ( 2 a ) under Cp*Rh(III) catalysis (Table 1).…”

“…As a result, there has been a growing interest in the application of such C−H functionalization events for synthesizing functionalized 1,2,3,4‐tetrahydroquinoline derivatives [9–11] . It is noteworthy that, with the assistance of N‐directing groups, 1,2,3,4‐tetrahydroquinoline C(8)−H bonds could readily undergo chlorination, [11a,o] arylation, [11b–e] acylation, [11g,h,p] amination, [11k,l] hydroxylation, [11m] and formylmethylation [11n,q] under the catalysis of palladium, rhodium or ruthenium. However, regioselective C8−H alkenylation and alkylation of 1,2,3,4‐tetrahydroquinolines have been sporadically investigated with only several examples known in the literature despite the potential utility of such products [12] .…”

Advancement of vinylene carbonate as a coupling partner in metal-catalyzed C–H functionalization

“…Furthermore, the Yan group elegantly employed the more cost-effective ruthenium catalyst to achieve this transformation, in which polar 2,2,2-trifluoroethanol solvent had a significant influence on accelerating reaction productivity. 45 The authors attempted to screen different coordinating groups, but only pyridine or pyrimidine was able to afford the desired product efficiently. And a possible pathway for this conversion was proposed as shown in Scheme 4.…”

Cobalt(III)-Catalyzed Directed C-7 Selective C–H Alkynylation of Indolines with Bromoalkynes

“…Among them, transition-metal-catalyzed C–H activation reaction represents a particularly powerful tool for the functionalization of the indolines due to its highly atom- and step-economy and environmental sustainability . Attractive methods involve directed C-7 C–H activation of indolines, such as alkylation, alkenylation, arylation, amination, acylation, sulfuration, halogenation, and cyanation/borylation . Despite impressive progress in the field, methods that consist of directed C-7 selective C–H alkynylation of indolines are rare and still remain a challenge of limited alkynylation reagents.…”