Carboiodanation of Arynes: Organoiodine(III) Compounds as Nucleophilic Organometalloids

Aryne Polymerization Enabled by Pyrazole-Induced Nucleophilic Aromatic Substitution

Despite the widespread use of arynes in organic synthesis, their polymerization remains a significant challenge due to the intrinsic instability and short lifetime of aryne intermediates. Here, we report a method for aryne polymerization using a simple organonucleophile, N-arylpyrazole, as an initiator. This polymerization proceeds via a unique pyrazole-induced nucleophilic aromatic substitution mechanism, facilitating the formation of poly(ortho-arylene)s with narrow polydispersity and well-defined structures. The high chemical stability of N-arylpyrazole allows for a broader scope of applications, including aryne polymerization at the side chain of preformed polymers (graft polymerization) and the synthesis of star-shaped poly(ortho-arylene)s.

Diazomethyl-λ3-iodane meets aryne: dipolar cycloaddition and C-to-N iodane shift leading to indazolyl-λ3-iodanes

Diazomethyl-λ3-iodanes have recently emerged as carbyne equivalents in organic synthesis, enabling the construction of multi-substituted carbon centers through strategic sequential activation of the diazo and iodane functional groups. Distinct from such reaction modes, we report here on the reactivity of diazomethyl-λ3-iodanes as iodane-bound 1,3-dipoles toward arynes. Equipped with bis(trifluoromethyl)benzyl alcohol-based benziodoxole (BX) moiety, diazomethyl-λ3-iodanes undergo annulation with arynes generated from ortho-silylaryl triflates and cyclic diarylhalonium salts, resulting in indazolyl-λ3-iodanes through [3 + 2] cycloaddition and carbon-to-nitrogen iodane migration. DFT calculations reveal that diazomethyl-BX prefers [3 + 2] cycloaddition with aryne over aryne insertion into the carbon-iodine(iii) bond (carboiodanation) and that the subsequent iodane migration proceeds through two consecutive 1,5-iodane shifts. The utility of these indazolyl-BXs as indazole-transfer agents has been demonstrated by α-functionalization of N,N-dimethylaniline derivatives.

Hexadehydro Diels-Alder/Alkynyliodanation Cascade: A Highly Regioselective Entry to Polycyclic Aromatics

We report here a cascade process integrating the hexadehydro Diels-Alder (HDDA) reaction with alkynyliodanation, enabling efficient synthesis of highly substituted aryl-λ3-iodanes. Heating a mixture of a tetrayne and an alkynylbenziodoxole induces regioselective insertion of the tetrayne-derived aryne into the alkynyl-iodine(III) bond, yielding a 1,4-dialkynyl-2-iodanyl-3-aryl(or alkyl)benzene derivative. The unique regiochemistry facilitates subsequent π-extension, allowing divergent access to polyaromatic frameworks, such as helicenes and cyclopenta[cd]pyrenes, underscoring the utility of aryne carboiodanation in complex aromatic synthesis.

Potassium Tetraiodatoiodate(III) Iodate(V): A Nonlinear Optical Crystal with Exceptional Second-Harmonic Generation and Full-Wavelength Phase Matching

The development of nonlinear optical materials with large nonlinear optical susceptibilities, wide transmission ranges, and comprehensive full-wavelength phase matching capabilities remains a significant challenge. In this study, we synthesized a novel potassium tetraiodatoiodate(III) iodate(V) via an in-situ reduction and complexation reaction. The resulting compound, K2[IIII(IVO3)4]IVO3, exhibits exceptional second-harmonic generation responses (21.6KH2PO4 at 1064 nm, 1.0KTiOPO4 at 2050 nm), a wide transparency range from the visible to the mid-infrared wavelengths (0.37-6.05 and 7.03-13.40 µm), and a high birefringence (0.358 at 543 nm) to achieve full-wavelength phase matching. These properties are primarily ascribed to the synergistic substantial hyperpolarizability and polarizability anisotropy exhibited by the [IIII(IVO3)4]- complex ions, which comprise square-planar coordinated trivalent iodine and optimally arranged iodate ligands. This study demonstrates the pivotal role of nonmetallic cation centered coordination entities in influencing linear and nonlinear optical properties, a discovery that has significant implications for the development of innovative inorganic functional materials.

Development and Applications of an Amide Linchpin Reagent

Linchpin reagents are building blocks that can be chemoselectively functionalized to afford products with a common, useful functional group. In this work, we describe the development and validation of the first amide linchpin reagent and demonstrate its use as a doubly electrophilic building block for the synthesis of a variety of amides, including challenging classes. The linchpin reagent was first functionalized via rhodium-catalyzed electrophilic amination. Selected masked C-isocyanate products were then further derivatized with Grignard reagents to produce secondary amides, or tertiary amides if an alkylating agent was added subsequently. The success of this sequence relies on fully controlled reactivity at each electrophilic site, first exploiting the weak N-O bond and then, the ability to form the free isocyanate intermediate in situ. The overall transformation proceeds with high chemoselectivity, demonstrating the ability of this new linchpin reagent to form amides through atypical bond construction. Finally, the potential of this reagent as a more broadly applicable NCO linchpin is demonstrated by the formation of lactams and unsymmetrical ureas.

Bifunctional Lewis Base-Catalyzed (3 + 2) Cycloadditions of Pyrazolone-Derived MBH Carbonates with Arynes

The (3 + 2) cycloaddition of arynes with allylic ylides remains a formidable challenge because both intermediates are highly reactive and prone to spontaneous quenching. Here, we report a (3 + 2) cycloaddition of pyrazolone MBH carbonates with arynes, enabling the efficient synthesis of diverse indene-fused spiropyrazolones. The key is employing a new bifunctional Lewis base catalyst to facilitate the cycloaddition of in situ generated allylic pyridinium ylides with arynes.

Harnessing the benzyne insertion consequence to enable π-extended pyrido-acridine and quinazolino-phenanthridine

Distinct protocols have been devised for the preparation of hybrid heterocyclic scaffolds like π-extended pyrido-acridines and quinazolino-phenanthridines duly materialized through Rh(III)- and Pd(II)-mediated catalytic courses commencing from acridine and quinazolimine scaffolds. Interestingly, the parent compounds (acridines and quinazolimines) are actualized from 2-aminobenzonitrile and anthranilic acid, where 2-aminobenzonitrile acts as the 1,4-dipolarophilic species and anthranilic acid as the benzyne precursor. The molecular assembly of acridine suggests the participation of two benzyne units. In addition, the structural motif of the quinazolimine ring features one benzyne unit. Further, indolizine ring containing the enaminonitrile skeleton upon exposure to benzyne forms an indolizine fused quinoline ring, decorated with three benzyne units.

Amino- and Alkoxybenziodoxoles: Facile Preparation and Use as Arynophiles

We report here on the facile synthesis of amino- and alkoxy-λ3-iodanes supported by a benziodoxole (BX) template and their use as arynophiles. The amino- and alkoxy-BX derivatives can be readily synthesized by reacting the respective amines or alcohols with chlorobenziodoxole in the presence of a suitable base. Unlike previously known nitrogen- and oxygen-bound iodane compounds, which have primarily been employed as electrophilic group transfer agents or oxidants, the present amino- and alkoxy-BX reagents manifest themselves as nucleophilic amino and alkoxy transfer agents toward arynes. This reactivity leads to the aryne insertion into the N-I(III) or O-I(III) bond to afford ortho-amino- and ortho-alkoxy-arylbenziodoxoles, iodane compounds nontrivial to procure by existing methods. The BX group in these insertion products exhibits excellent leaving group ability, enabling diverse downstream transformations.

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

A stereoselective N-alkenylation of azoles with alkynes and iodine(III) electrophile is reported. The reaction between various azoles and internal alkynes is mediated by benziodoxole triflate as the electrophile in a trans-fashion, affording azole-bearing vinylbenziodoxoles in moderate to good yields. The tolerable azole nuclei include pyrazole, indazole, 1,2,3-triazole, benzotriazole, and tetrazole. The iodanyl group in the product can be leveraged as a versatile synthetic handle, allowing for the preparation of hitherto inaccessible types of densely functionalized N-vinylazoles.