Lithium phosphonate umpolung catalysts: Do fluoro substituents increase the catalytic activity?

Abstract

SummaryFluorinated and nonfluorinated phosphonates are employed as precatalysts in lithium phosphonate catalyzed cross benzoin couplings. Surprisingly, a decreased catalytic activity for the fluorinated precatalysts compared to the nonfluorinated systems is observed. Furthermore, the ring size of six, seven and nine membered ring catalysts appears not to be crucial for their catalytic activity.

Bis(2,2,2 trifluoroethyl) Phosphonate as a Convenient Precursor for the Synthesis of H-Phosphonates

“…2-Hydro-2-oxo-4,7-dihydro-1,3,2-benzodioxaphosphepine ( 7 ) (reaction time: 15 min); colorless needles; yield: 178 mg (0.97 mmol; 97%); 1 H NMR (400 MHz, Chloroform-d) δ 7.42–7.32 (m, 4H), 7.32–7.20 (m, 4H), 7.03 (d, J = 702.3 Hz, 1H), 5.40 (dd, J = 18.0, 13.9 Hz, 2H), 5.18 (dd, J = 15.6, 13.9 Hz, 2H) ppm; 13 C NMR (101 MHz, Chloroform-d) δ 134.7, 129.1, 128.6, 66.3 (d, J = 6 Hz) ppm; 31 P NMR (162 MHz, Chloroform-d) δ 13.09 (dtt, J = 702.3 Hz, J = 17.7, 15.7 Hz) ppm; HRMS–ESI (Micro-Tof, m / z ): [M + Na] + calcd for C 8 H 9 NaO 3 P, 207.0182; found, 207.0178; analytical data are in agreement with the literature [ 9 ].…”

“…Based on their tautomerism between the P(III) phosphite form and the P(V) H-phosphonate form, they can either react as nucleophiles or as electrophiles [ 2 , 3 ]. Their broad use spans from building blocks for the formation of compounds, such as aminophosphonates [ 4 ], bisphosphonates [ 5 ], phosphates [ 6 ], nucleotides [ 7 ], to their application as catalysts [ 8 , 9 ] and ligands [ 10 ]. The synthesis of H-phosphonates is typically accomplished by direct substitution from phosphorous trichloride, either in a tert-butanolysis reaction, with excess alcohol or in the presence of a base.…”

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

“…The X-ray crystal structure also reveals that an alternative formation of intra- and intermolecular hydrogen bonds [intra- D(OH···O): 1.951(3) Å; inter- D(OH···O): 1.822(3) Å] led to an enantiomerically pure infinite helical supramolecular structure. In contrast, only a dimeric structure was observed for the corresponding racemic mixture [39]. In our case, atropisomerization from ( M )-( S , S ) to ( P )-( S , S ) was not observed in solution.…”

Synthesis and characterization of novel flavonoid derivatives via sequential phosphorylation of quercetin

“…The carbonyl group at position 4 which lies in conjugation with C -C double bond at position 2 and 3 deprives the oxygen at position 3 electrons reducing the back-bonding ability which is consistent with Bent rule of electron withdrawing substituent requiring more p-character in the bonding orbital. [37][38] Similarly, the enol ether oxygen at position 1 further complicates the electronegativity contribution and therefore the phosphorus at position 3 on ring C will be more upfield as seen in QPPI 31 P NMR. On the other hand, the splitting pattern of proton signals in the 1 H NMR resonating Tetrahedron 10 around 5ppm indicates the presence of the two methylene groups on the benzyl ether groups attached to phosphorus center.…”