Ru(II)-Catalyzed Regioselective Redox-Neutral [4 + 2] Annulation of N-Chlorobenzamides with 1,3-Diynes at Room Temperature for the Synthesis of Isoquinolones

Herein, we report Ru(II)-catalyzed C-H/N-H bond functionalization of N-chlorobenzamides with 1,3-diynes via regioselective (4 + 2) annulation for the synthesis of isoquinolones under redox-neutral conditions at room temperature. This represents the first example of C-H functionalization of N-chlorobenzamides using an inexpensive and commercially available [Ru(p-cymene)Cl₂]₂ catalyst. The reaction is operationally simple, works in the absence of any silver additives, and is also applicable to a broad range of substrates with good functional group tolerance. The synthetic utility of the isoquinolone is demonstrated for the synthesis of bis-heterocycles consisting of isoquinolone-pyrrole and isoquinolone-isocoumarin scaffolds.

Development of 1,3-diynyl derivatives of noscapine as potent tubulin binding anticancer agents for the management of breast cancer

We developed 1,3-diynyl derivatives of noscapine (an opium alkaloid) through in silico combinatorial approach and screened out a panel of promising derivatives that bind tubulin and display anticancer activity. The selected derivatives such as 9-4-^tBu-Ph-Diyne (20p), 9-3,4-Di-Cl-Diyne (20k) and 9-3,4-Di-F-Diyne (22s) noscapinoids revealed improved predicted binding energy of -6.676 kcal/mol for 20p, -7.294 kcal/mol for 20k and -7.750 kcal/mol for 20s respectively in comparison to noscapine (-5.246 kcal/mol). These 1,3-diynyl derivatives (20p, 29k and 20s) were strategically synthesized in high yields by regioselective modification of noscapine scaffold and HPLC purified (purity is >96%). The decrease in intrinsic fluorescence of purified tubulin to 8.39%, 17.39% and 25.47% by 20p, 20k and 20s respectively, compared to control suggests their binding capability to tubulin. Their cytotoxicity activity was validated based on cellular studies using two human breast adenocarcinoma (MCF-7 and MDA-MB-231), a panel of primary breast tumor cells and one normal human embryonic kidney cell (293 T). The 1,3-diynyl noscapinoids, 20p, 20k and 20s inhibited cellular proliferation in all the cancer cells that ranged between 6.2 and 38.9 µM, without affecting the normal healthy cells (cytotoxicity is <5% at 100 µM). Further, these novel derivatives arrest cell cycle in the G2/M-phase, followed by induction of apoptosis to cancer cells. Thus, we conclude that 1,3-diynyl-noscapinoids have great potential to be a novel therapeutic agent for breast cancers.Communicated by Ramaswamy H. Sarma.

Hydroelementation of diynes

This review highlights the hydroelementation reactions of conjugated and separated diynes, which depending on the process conditions, catalytic system, as well as the type of reagents, leads to the formation of various products: enynes, dienes, allenes, polymers, or cyclic compounds. The presence of two triple bonds in the diyne structure makes these compounds important reagents but selective product formation is often difficult owing to problems associated with maintaining appropriate reaction regio- and stereoselectivity. Herein we review this topic to gain knowledge on the reactivity of diynes and to systematise the range of information relating to their use in hydroelementation reactions. The review is divided according to the addition of the E-H (E = Mg, B, Al, Si, Ge, Sn, N, P, O, S, Se, Te) bond to the triple bond(s) in the diyne, as well as to the type of the reagent used, and the product formed. Not only are the hydroelementation reactions comprehensively discussed, but the synthetic potential of the obtained products is also presented. The majority of published research is included within this review, illustrating the potential as well as limitations of these processes, with the intent to showcase the power of these transformations and the obtained products in synthesis and materials chemistry.

Rational design, chemical synthesis and cellular evaluation of novel 1,3-diynyl derivatives of noscapine as potent tubulin binding anticancer agents

We present a new class of derivatives of noscapine, 1,3-diynyl-noscapinoids of an antitussive plant alkaloid, noscapine based on our in silico efforts that binds tubulin and displays anticancer activity against a panel of breast cancer cells. Structure-activity analyses pointed the C-9 position of the isoquinoline ring which was modified by coupling of 1,3-diynyl structural motifs to rationally design and screened a series of novel 1,3-diynyl-noscapinoids (20-22) with robust binding affinity with tubulin. The selected 1,3-diynyl-noscapinoids, 20-22 revealed improved predicted binding energy of -6.568 kcal/mol for 20, -7.367 kcal/mol for 21 and -7.922 kcal/mol for 22, respectively in comparison to the lead molecule (-5.246 kcal/mol). These novel derivatives were chemically synthesized and validated their anticancer activity based on cellular studies using two human breast adenocarcinoma, MCF-7 and MDAMB-231, as well as with a panel of primary breast cancer cells isolated from patients. Interestingly, all these derivatives inhibited cellular proliferation in all the cancer cells that ranged between 6.2 to 38.9 μM, which is 6.7 to 1.5 fold lower than that of noscapine. Unlike previously reported derivatives of noscapine that arrests cells in the S-phase, these novel derivatives effectively inhibit proliferation of cancer cells, arrests cell cycle in the G2/M-phase followed by apoptosis and appearance of apoptotic cells. Thus, we conclude that 1,3-diynyl-noscapinoids have great potential to be a novel therapeutic agent for breast cancers.

Gold-Catalyzed Oxidative Coupling of Alkynes toward the Synthesis of Cyclic Conjugated Diynes

A gold-catalyzed oxidative coupling of alkynes was developed as an efficient approach for the synthesis of challenging cyclic conjugated diynes (CCD). Compared to the classical copper-promoted oxidative coupling reaction of alkynes, this gold-catalyzed process exhibits a faster reaction rate due to the rapid reductive elimination from the Au(III) intermediate. This unique reactivity thus allowed a challenging diyne macrocyclization to take place in high efficiency. Condition screening revealed a [(n-Bu)₄N]⁺[Cl-Au-Cl]^- salt as the optimal pre-catalyst. Macrocycles with ring size between 13 to 28 atoms were prepared in moderate to good yields, which highlighted the broad substrate scope of this new strategy. Furthermore, the synthetic utilities of the cyclic conjugated diynes for copper-free click chemistry have been demonstrated, which showcased the potential application of this strategy in biological systems.