Catalytic C(sp2)-C(sp3) Bond Formation of Methoxyarenes by the Organic Superbase t-Bu-P4

Phosphazene base-catalyzed telescopic three-component reaction involving 1,1-difunctionalization of electron-deficient alkenes

Phosphazene base, P2-tBu, efficiently catalyzed the telescopic three-component reaction of diethyl phosphite, cinnamonitrile derivatives, and N-Boc imines, providing β-aminophosphonates having a tetrasubstituted carbon in a highly diastereoselective manner. The reaction involves the little-known 1,1-difunctionalization of an electron-deficient alkene, offering a new format for the three-component reaction under Brønsted base catalysis.

Catalytic Generation of Benzyl Anions from Aryl Ketones Utilizing [1,2]-Phospha-Brook Rearrangement and Their Application to Synthesis of Tertiary Benzylic Alcohols

A synthetic method of tertiary alcohols was developed based on the formal umpolung addition of aryl ketones with electrophiles utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. The addition reaction of α-hydroxyphosphonates, derived from alkyl aryl- and diaryl ketones, with electrophiles such as phenyl vinyl sulfone, afforded phosphates having a tertiary alkyl group, which were readily convertible to the corresponding tertiary benzylic alcohols. This operationally simple protocol provides efficient complementary access to tertiary alcohols that are difficult to synthesize by conventional methods.

Catalytic Concerted SNAr Reactions of Fluoroarenes by an Organic Superbase

We herein propose that the catalytic concerted SNAr reaction is a powerful method to prepare functionalized aromatic scaffolds. Classic stepwise SNAr reactions involving addition/elimination processes require the use of electron-deficient aromatic halides to stabilize Meisenheimer intermediates, despite their widespread use in medicinal chemistry research. Recent efforts have been made to develop concerted SNAr reactions involving a single transition state, allowing the use of electron-rich substrates based on the use of stoichiometric amounts of strong bases or reactive nucleophiles. This study demonstrates that, without the use of such reagents, the organic superbase t-Bu-P4 efficiently catalyzes the concerted SNAr reactions of aryl fluorides regardless of their electronic nature. The key to establishing this system is the dual activation of aryl fluoride and anionic nucleophiles by the t-Bu-P4 catalyst. Furthermore, this catalysis allows excellent functional group tolerance, utilization of diverse nucleophiles, and late-stage functionalization of bioactive compound derivatives. These findings make possible diverse applications in chemical synthesis and pharmaceutical development.

Metal-Free, Hindered, Regioselective Access to Multifunctional Groups Diarylamines via SN Ar Substitution of P-Nitroso Aromatic Methyl Ether by Arylamines

Multifunctional groups diarylamines, an innovative product, efficiently produced from arylamines and p-nitrosoanisole derivatives by intermolecular SN Ar under weak acid conditions. This SN Ar proceeds under mild reaction conditions, and more significantly, the substrates involved do not necessarily require strong electron-withdrawing groups. Moreover, this SN Ar is characterized by resistance to space crowding, tolerance to halogen and nitroso functional groups, and high regioselectivity. Mechanistic observations suggest that the SN Ar is the result of the transfer of the positive charge center of the protonated nitroso group to the p-methoxy group.

Transition-Metal Free C-C Bond Cross-Coupling of Aryl Ethers with Diarylmethanes

We describe a general and efficient transition-metal free C-C bond cross-coupling of (hetero)aryl ethers and diarylmethanes via C(sp²)-O bond cleavage. The coupling reactions mediated by KHMDS proceeded well with high efficiency, broad substrate scope, and good functional group tolerance. The robustness and practicability of this protocol also have been demonstrated by easy gram-scale preparation and diversified product derivatization.

Defluorinative Transformation of (2,2,2-Trifluoroethyl)arenes Catalyzed by the Phosphazene Base t-Bu-P2

In this study, we demonstrated that 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ5,4λ5-catenadi(phosphazene) (t-Bu-P2) catalyzes the defluorinative functionalization reactions of (2,2,2-trifluoroethyl)arenes with alkanenitriles to produce monofluoroalkene products. The reaction proceeds through HF elimination from a (2,2,2-trifluoroethyl)arene to form a gem-difluorostyrene intermediate, which is followed by nucleophilic addition of an alkanenitrile and elimination of a fluoride anion. The catalysis is compatible with a variety of functional groups.

Highly selective α-aryloxyalkyl C-H functionalisation of aryl alkyl ethers

We report highly selective photocatalytic functionalisations of alkyl groups in aryl alkyl ethers with a range of electron-poor alkenes using an acridinium catalyst with a phosphate base and irradiation with visible light (456 nm or 390 nm). Experiments indicate that the reaction operates via direct single-electron oxidation of the arene substrate ArOCHRR' to its radical cation by the excited state organic photocatalyst; this is followed by deprotonation of the ArOC-H in the radical cation to yield the radical ArOC˙RR'. This radical then attacks the electrophile to form an intermediate alkyl radical that is reduced to complete the photocatalytic cycle. The oxidation step is selective for activated arenes (ArOR) over their non-activated counterparts and the subsequent deprotonation of the methoxy group affords the α-aryloxyalkyl radical that leads to a wide range of functionalised products in good to excellent yield.

Decyanation-(hetero)arylation of malononitriles to access α-(hetero)arylnitriles

Quaternary α-(hetero)arylnitriles are desirable biologically relevant products, however the existing methods for their synthesis can be unselective or require the use of undesirable reagents, such as cyanide salts. Herein we report a one-pot method for transnitrilation-mediated decyanation-metalation of disubstituted malononitriles, followed by treatment with (hetero)aryl electrophiles to access quaternary α-(hetero)arylnitrile products. A number of products were prepared using this method (34 examples, 27-99% yield). This method highlights the usefulness of malononitriles as precursors for alkylnitrile-containing compounds.

Organic superbase t-Bu-P4-catalyzed demethylations of methoxyarenes

The organic superbase t-Bu-P4 catalyzes the demethylation reactions of methoxyarenes in the presence of alkanethiol and hexamethyldisilazane.

The organocatalytic synthesis of perfluorophenylsulfides via the thiolation of trimethyl(perfluorophenyl)silanes and thiosulfonates

The organic superbase t-Bu-P₄-catalyzed direct thiolation of trimethyl(perfluorophenyl)silanes and thiosulfonates was developed. Yields of perfluorophenylsulfides of up to 97% under catalysis of 5 mol% t-Bu-P₄ were achieved. This method was shown to provide an efficient way to construct the perfluorophenyl-sulfur bond under mild metal-free reaction conditions.

Organocatalytic aminocarbonylation of α,β-unsaturated ketones with N,N-dimethyl carbamoylsilane

Schwesinger's superbase can efficiently activate the Si–CONMe₂ bond and initiate the aminocarbonylation of α,β-unsaturated ketones and N,N-dimethyl carbamoylsilane.