Heterocyclic compounds are important organic compounds and have emerged as key scaffolds in numerous drugs, natural products, vitamins, biologically and pharmaceutically active compounds. Over the ...past few decades, the development of versatile methodologies employing propargylic alcohols as synthons for the construction of heterocyclic skeletons has attracted great attention from synthetic chemists. In this review, recent developments in the cascade cyclization of propargylic alcohols with diverse nucleophiles to construct heterocyclic compounds are summarized. According to the types of nucleophiles, these reactions can be divided into four categories: 1) Reactions involving C‐nucleophiles to capture allenyl carbocation; 2) Reactions involving O, S‐nucleophiles to capture allenyl carbocation; 3) Reactions involving N, P‐nucleophiles to capture allenyl carbocation; 4) Reactions involving halo‐nucleophiles to capture allenyl carbocation.
In the last few years, the development of versatile methodologies to incorporate trifluoromethyl groups into organic molecules has attracted significant attention in synthetic chemistry. This review ...gives an overview over the development on the trifluoromethylation of alkynes, which have not been solely discussed before. Formation of diverse C(sp, sp2, sp3)CF3 bonds are all covered in this review.
Versatile methodologies for the incorporation of trifluoromethyl groups into organic molecules have attracted significant attention in synthetic chemistry. This Minireview highlights the recent efforts on the development of trifluoromethylation of alkynes to construct various diverse C(sp, sp2, sp3)CF3 bonds by radical processes, or through transition‐metal catalysis by using nucleophilic or electrophilic trifluoromethylation reagents (see scheme).
Phosphonothioates, phosphinothioates and phosphorothioates are regarded as an important class of sulfur‐containing organophosphorus compounds. Because of the unique P(O)S−R group, these compounds ...have important biological activities and thus have been widely used in the fields of pharmaceuticals and pesticides. In recent years, the development of sulfur‐containing organophosphorus compounds by radical processes has attracted considerable attention in organophosphorus chemistry. Along these lines, in this review, the recent advances in the synthesis of sulfur‐containing organophosphorus compounds were systematically summarized. According to the different ways of generating radicals during the formation process of phosphonothioates, phosphinothioates and phosphorothioates, these transformations can be divided into four categories: (1) Oxidant or metal‐free promoted radical transformation to fabricate sulfur‐containing organophosphorus compounds; (2) Copper‐catalyzed radical transformation to produce sulfur‐containing organophosphorus compounds; (3) Photo‐induced radical transformation to prepare sulfur‐containing organophosphorus compounds; (4) Electro‐induced radical transformation to derive sulfur‐containing organophosphorus compounds.
Propargylic alcohols are regarded as a class of readily available and versatile synthons in organic synthesis. Due to their unique bifunctional character, the transformation of propargylic alcohols ...has been widely utilized as a powerful strategy for the construction of various functionalized frameworks over the past few decades. Recently, the radical transformation of propargylic alcohols has attracted considerable attention in synthetic chemistry. This review summarizes recent progress in the radical transformation of propargylic alcohols. Based on the different mechanisms of radical formation underlying these transformations, this review has been divided into four parts: (1) transition‐metal catalyzed radical transformation; (2) photo‐induced radical transformation; (3) electro‐induced radical transformation; and (4) metal‐free or oxidant‐mediated radical transformation of propargylic alcohols.
An electrocatalytic approach for the bromide‐mediated selenocyclization of N‐propargylamides with diselenides is described, providing a synthetic route for the synthesis of various seleno‐oxazoles in ...41–73% yields. The success of gram‐scale experiments demonstrate the potential value of this protocol in synthetic chemistry. Mechanistic investigations suggest that this selenocyclization protocol proceed through two possible pathways, including selenium cation and radical processes.
A copper‐catalyzed difunctionalizing trifluoromethylation of activated alkynes with the cheap reagent sodium trifluoromethanesulfinate (NaSO2CF3 or Langlois’ reagent) has been developed incorporating ...a tandem cyclization/dearomatization process. This strategy affords a straightforward route to synthesis of 3‐(trifluoromethyl)‐spiro4.5trienones, and presents an example of difunctionalization of alkynes for simultaneous formation of two carbon–carbon single bonds and one carbon–oxygen double bond.
Spiro mania: A copper‐catalyzed difunctionalizing trifluoromethylation of activated alkynes with the cheap reagent NaSO2CF3 has been reported, affording a series of 3‐trifluoromethyl spiro4.5trienones through a tandem cyclization/dearomatization process. In this alkyne difunctionalization process, two carbon–carbon bonds and one carbon–oxygen double bond are simultaneously formed.
We present a highly efficient and practical method for synthesizing
-dibromo 1,3-oxazines through 6-
cyclization of propargylic amides, using
-bromosuccinimide (NBS) as an electrophilic source. The ...metal-free reaction can be conducted under mild conditions with good functional group compatibility, delivering excellent yields of the desired products. Mechanistic studies suggest that the reaction proceeds
a double electrophilic attack by NBS on the propargylic amide substrate.
Abstract Manganese (Mn) is the third most abundant transition metal on Earth and is known for its exceptional biocompatibility. The development of novel catalytic mode for Mn is of great significance ...to advancing organic synthesis. In this study, the first manganese (Mn)‐catalyzed 2+2+2 cycloaddition of alkynes is achieved with the aid of visible‐light photoredox catalysis. Photoredox catalysis is proposed to promote the transformation by in situ reduction of high‐valent Mn(II) complex to Mn(0) species, thereby initiating the reaction. Additionally, a photooxidation‐induced reductive ellimination step is also suggested. This system is further distinguished by its notable tolerance towards both terminal and internal alkynes as counterparts of diynes.
A facile and general approach was developed for the efficient construction of functionalized bromoquinolines by the dehydrogenation of tetrahydroquinolines using NBS as the electrophile and as ...oxidant. The cascade transformation proceeded with good functional group tolerance under metal-free conditions with a short reaction duration. Various tetrahydroquinolines bearing either electron-rich or electron-deficient groups at different positions were successfully converted into the corresponding target products in moderate to high yields under mild conditions. It is worth noting that the obtained polybromoquinolines could further undergo classic metal-catalyzed cross-coupling reactions with good regioselectivity. The Sonagashira coupling reaction occurred regioselectively in the C-6 position of the obtained products followed by a Suzuki coupling reaction to give multifunctionalized quinolines. The mechanism indicated that electrophilic bromination/radical dehydrogenation sequences occurred in one pot.
An efficient and practical bromination/dehydrogenation of tetrahydroquinolines was developed for the one-pot construction of polybromoquinolines under mild conditions. NBS not only acts as an electrophile, but also as an oxidant in this reaction.
Herein, the first example of visible‐light‐driven, cobalt‐catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using IrdF(CF3)ppy2(dtbbpy)PF6 as ...photosensitizer, CoBr2/n‐Bu3P as proton‐reducing catalyst, and i‐Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over‐reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single‐electron transfer process and controlling the stereoselectivity via an energy transfer process.
