RESUMEN
Large quantities of fluorinated gases are generated as intermediates or byproducts from fluorinated polymer production annually, and they are effective ozone depleting substances or greenhouse gases. On the other hand, the incorporation of fluoroalkyl groups into drug molecules or bioactive compounds has been shown to enhance biological properties such as the bioavailability, binding selectivity, and metabolic stability. Extraction of fluoroalkyl sources, including trifluoromethyl and difluoromethyl groups, from the fluorinated gases is highly desirable, yet challenging under regular batch reaction conditions. Flow chemistry is an emerging and promising technique to address long-standing challenges in gas-liquid batch reactions such as insufficient interfacial contact and scalability issues. In this review, we highlight recent advances in continuous flow strategies toward enabling the use of fluorinated greenhouse gases in organic synthesis.
RESUMEN
The base metal-catalyzed C-N cross-coupling of bulky α,α,α-trisubstituted primary alkylamines with (hetero)aryl electrophiles represents a challenging and under-developed class of transformations that is of significant potential utility, including in the synthesis of lipophilic active pharmaceutical ingredients. Herein, we report that a new, air-stable Ni(II) pre-catalyst incorporating the optimized ancillary ligand PhPAd-DalPhos enables such transformations of (hetero)aryl chloride, bromide, and tosylate electrophiles to be carried out for the first time with substrate scope rivalling that achieved using state-of-the-art Pd catalysts, including room temperature cross-couplings of (hetero)aryl chlorides that are unprecedented for any catalyst (Pd, Ni, or other).
RESUMEN
The use of (L)Ni( o-tolyl)Cl precatalysts (L = PAd-DalPhos or CyPAd-DalPhos) enables the C( sp2)-O cross-coupling of primary, secondary, or tertiary aliphatic alcohols with (hetero)aryl electrophiles, including unprecedented examples of such nickel-catalyzed transformations employing (hetero)aryl chlorides, sulfonates, and pivalates. In addition to offering a competitive alternative to palladium catalysis, this work establishes the feasibility of utilizing ancillary ligation as a complementary means of promoting challenging nickel-catalyzed C( sp2)-O cross-couplings, without recourse to precious-metal photoredox catalytic methods.
RESUMEN
The first nickel-catalyzed N-arylation of amides with (hetero)aryl (pseudo)halides is reported, enabled by use of the air-stable pre-catalyst (PAd-DalPhos)Ni(o-tolyl)Cl (C1). A range of structurally diverse primary amides and lactams were cross-coupled successfully with activated (hetero)aryl chloride, bromide, triflate, tosylate, mesylate, and sulfamate electrophiles.
RESUMEN
The first examples of acetone mono-α-arylation at room temperature are described, enabled by use of a [Pd(cinnamyl)Cl]2 /JosiPhos catalyst system. (Hetero)aryl chloride, bromide, and iodide electrophiles featuring or lacking ortho-substitution, and comprising a range of functionalities (e.g., alkoxy, cyano, fluoro, trifluoromethyl, or alkenyl) and heteroaryl motifs (e.g., pyrrole, pyridine, isoquinoline, quinoline, quinaldine, (benzo)thiophene, benzothiazole, or benzodioxole) were successfully accommodated. Proof-of-principle experiments confirm that other (hetero)aryl methyl ketones can also be employed in such room temperature mono-α-arylations. The established substrate scope is the most extensive reported to date for acetone mono-α-arylation under any conditions, and more generally represents the first room temperature ketone mono-α-arylations employing a structurally diverse set of (hetero)aryl chlorides.
RESUMEN
Structurally diverse (hetero)aryl chloride, bromide, and tosylate electrophiles were employed in the Ni-catalyzed monoarylation of ammonia, including chemoselective transformations. The employed JosiPhos/[Ni(cod)2] catalyst system enables the use of commercially available stock solutions of ammonia, or the use of ammonia gas in these reactions, thereby demonstrating the versatility and potential scalability of the reported protocol. Proof-of-principle experiments established that air-stable [(JosiPhos)NiCl2] precatalysts can be employed successfully in such transformations.
RESUMEN
Palladium-catalysed C(sp(2))-N cross-coupling (that is, Buchwald-Hartwig amination) is employed widely in synthetic chemistry, including in the pharmaceutical industry, for the synthesis of (hetero)aniline derivatives. However, the cost and relative scarcity of palladium provides motivation for the development of alternative, more Earth-abundant catalysts for such transformations. Here we disclose an operationally simple and air-stable ligand/nickel(II) pre-catalyst that accommodates the broadest combination of C(sp(2))-N coupling partners reported to date for any single nickel catalyst, without the need for a precious-metal co-catalyst. Key to the unprecedented performance of this pre-catalyst is the application of the new, sterically demanding yet electron-poor bisphosphine PAd-DalPhos. Featured are the first reports of nickel-catalysed room temperature reactions involving challenging primary alkylamine and ammonia reaction partners employing an unprecedented scope of electrophiles, including transformations involving sought-after (hetero)aryl mesylates for which no capable catalyst system is known.