Photocatalytic Alkylation of α-(Trifluoromethyl)Styrenes with Potassium Xanthogenates

A protocol for the coupling of potassium xanthogenates with α-(trifluoromethyl)styrenes in the presence of triethyl phosphite is reported. The reaction is carried out under blue light irradiation in the presence of organic photocatalyst 3DPAFIPN. The reaction proceeds via formation of alkyl radicals from readily available xanthogenate salts via oxidative desulfurization and cleavage of the carbon–oxygen bond assisted by triethyl phosphite.

Catalytic phosphonylation of C=X electrophiles

A method for the catalytic phosphonylation of C = X electrophiles has been developed. Pyridinium perchlorate is an effective catalyst for the phosphonylation reaction of trialkyl phosphites with various electrophiles C = X (X = O, S, N). The reaction leads to the formation of corresponding α-substituted phosphonates in high yields. The reaction leading to the formation of bisphosphonates represents the highest interest. It was found that the nucleo philic attack of triethyl phosphite on the electron-deficient carbon of the C = X group leads to the formation of beta ine, which reacts with pyridinium perchlorate to form alkoxyphosphonium perchlorate and pyridine. Quasiphosphonium salt is unstable and decomposes to form phosphonate, alkene, and perchloric acid, which reacts with pyridine to regenerate pyridinium perchlorate. The intermediate formed from the pyridinium halide decomposes to form alkyl halide. The general strategy of the proposed method for introducing phosphonate groups into a polyprenyl mole cule consisted in the sequential treatment of hydroxyl-containing a compound with the Swern reagent with the con version of the C—OH group into a carbonyl one. Subsequent phosphonylation of the carbonyl-containing interme diate with the reagent (EtO)3P/[PyH] + ClO 4– leads to the formation of hydroxyalkylbisphosphonate. The synthe sized prenyl bisphosphonates have a pronounced biological activity. These include, for example, enolpyruvylshikimate-3- phosphate synthase (EPSP), farnesyl protein transferase (FPTase), as well as HIV protease, which are of interest as potential biologically active substances.

Facile Access to 3,4-Disubstituted 2H-Chromenes via Domino [4+2] Annulation

A highly efficient synthetic route to polysubstituted 2H-chromenes was developed utilizing a domino O-alkylation/intramolecular Horner–Wadsworth–Emmons (HWE) olefination of diarylmethylphosphonates, which were readily accessed via Lewis acid mediated one-pot three-component coupling of aldehydes, phenols, and triethyl phosphite.

Synthesis of 1,2,3-Triazole-Containing Furanosyl Nucleoside Analogs and Their Phosphate, Phosphoramidate or Phoshonate Derivatives as Potential Sugar Diphosphate or Nucleotide Mimetics

<p>The synthesis of a variety of novel, rather stable and potentially bioactive nucleoside analogs and nucleotide mimetics based on xylofuranose scaffolds and comprising a 1,2,3-triazole moiety as a surrogate for a nucleobase or a phosphate group is reported. Isonucleosides embodying a 3-<i>O</i>-(benzyltriazolyl)methyl moiety at C-3 were accessed by using the Cu(I)-catalyzed “click” 1,3-dipolar cycloaddition between 3-<i>O</i>-propargyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranose and benzyl azide as the key step. Related isonucleotides comprising a phosphate or a phosphoramidate moiety at C-5 were obtained via 5-<i>O</i>-phosphorylation of acetonide-protected 3-<i>O</i>-propargyl xylofuranose followed by “click” cycloaddition or by Staudinger reaction of a 5ʹ-azido <i>N</i>-benzyltriazole isonucleoside with triethyl phosphite, respectively. Hydroxy, amino- or bromomethyl triazole 5ʹ-isonucleosides were synthesized through thermal cycloaddition between 5-azido 3-<i>O</i>-benzyl/dodecyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranoses and propargyl alcohol, propargylamine or propargyl bromide, respectively. The regiochemical outcome of the cycloaddition reactions was influenced by nature of the alkyne hetero substituent (alkyne CH₂X substituent). The 5´-isonucleosides were converted into their [(xylofuranos-5-yl)triazolyl]methyl phosphate, phosphoramidate and phosphonate derivatives as prospective sugar diphosphate mimetics by an appropriate method involving treatment with diethyl phosphorochloridate or a Michaelis-Arbuzov reaction. 4-Phosphonomethyl-1-xylofuranos-5ʹ-yl triazoles were converted into 1,2-<i>O</i>-acetyl glycosyl donors and subsequently subjected to nucleosidation with uracil leading to the corresponding uracil nucleoside 5ʹ-(triazolyl)methyl phosphonates, whose structure potentially mimics that of a nucleoside diphosphate. </p> <p><b> </b></p>

Synthesis of 1,2,3-Triazole-Containing Furanosyl Nucleoside Analogs and Their Phosphate, Phosphoramidate or Phoshonate Derivatives as Potential Sugar Diphosphate or Nucleotide Mimetics

<p>The synthesis of a variety of novel, rather stable and potentially bioactive nucleoside analogs and nucleotide mimetics based on xylofuranose scaffolds and comprising a 1,2,3-triazole moiety as a surrogate for a nucleobase or a phosphate group is reported. Isonucleosides embodying a 3-<i>O</i>-(benzyltriazolyl)methyl moiety at C-3 were accessed by using the Cu(I)-catalyzed “click” 1,3-dipolar cycloaddition between 3-<i>O</i>-propargyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranose and benzyl azide as the key step. Related isonucleotides comprising a phosphate or a phosphoramidate moiety at C-5 were obtained via 5-<i>O</i>-phosphorylation of acetonide-protected 3-<i>O</i>-propargyl xylofuranose followed by “click” cycloaddition or by Staudinger reaction of a 5ʹ-azido <i>N</i>-benzyltriazole isonucleoside with triethyl phosphite, respectively. Hydroxy, amino- or bromomethyl triazole 5ʹ-isonucleosides were synthesized through thermal cycloaddition between 5-azido 3-<i>O</i>-benzyl/dodecyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranoses and propargyl alcohol, propargylamine or propargyl bromide, respectively. The regiochemical outcome of the cycloaddition reactions was influenced by nature of the alkyne hetero substituent (alkyne CH₂X substituent). The 5´-isonucleosides were converted into their [(xylofuranos-5-yl)triazolyl]methyl phosphate, phosphoramidate and phosphonate derivatives as prospective sugar diphosphate mimetics by an appropriate method involving treatment with diethyl phosphorochloridate or a Michaelis-Arbuzov reaction. 4-Phosphonomethyl-1-xylofuranos-5ʹ-yl triazoles were converted into 1,2-<i>O</i>-acetyl glycosyl donors and subsequently subjected to nucleosidation with uracil leading to the corresponding uracil nucleoside 5ʹ-(triazolyl)methyl phosphonates, whose structure potentially mimics that of a nucleoside diphosphate. </p> <p><b> </b></p>

Intermolecular Phosphite-Mediated Radical Desulfurative Alkene Alkylation Using Thiols

<div><div><div><p>We report herein the development of an S-atom transfer process using triethyl phosphite as the S-atom acceptor that allows thiols to serve as precursors of C-centered radials. A range of functionalized and electronically unbiased alkenes including those containing common heteroatom-based functional groups. This process is driven by the exchange of relatively weak S-H and C-S bonds of aliphatic thiols for C-H, C-C, and S-P bonds of the products formed.</p></div></div></div>