Addition of optically pure H-phosphinate to ketones: selectivity, stereochemistry and mechanism

Abstract

Aromatic methyl ketones and cyclic asymmetric ketones underwent hydrophosphorylation with P-stereogenic H-P species in the presence of potassium carbonate to produce P,C-stereogenic tertiary α-hydroxyl phosphinates in excellent yields with up to 99 : 1 dr. The diastereoselectivity was induced by a reversible conversion of less stable stereomer of product to that of a more stable one via an equilibrium, which was confirmed by aldehyde/ketone exchanging reaction. Toward the exchange, aliphatic or aldehyde carbonyl were more active than aromatic or ketone carbonyls, respectively. The stability difference between the two diastereomers was controlled by the sizes of substituents linking to phosphorus or α-carbon.

Synthesis and NMR Analysis of 1,4‐Disubstituted 1,2,3‐Triazoles Tethered to Pyridine, Pyrimidine, and Pyrazine Rings

“…[12,37] In compound series 3, the 15 (Table 5, entries [12][13][14][15][16][17]. Unexpectedly, in contrast to compounds 3, the triazole N-1 and N-3 atoms in compounds 4 are more shielded than N-2 (compare Table 5, entries 2, 3, and 6 with entries 13, 14, and 17, respectively).…”

“…This is interpreted as being due to a response by the pyridine ring to the π-donation of the triazole N-1 nitrogen atom, and to a lesser extent to the weakly π-excessive nature [41] of the triazole ring. The effect of the latter is seen in the 4-(2-pyridyl) triazole series 4 (δ = 302 ppm, Table 5, entries [12][13][14][15][16][17], where the triazole C-4 atom is bound to the pyridine C-2Ј atom, resulting in an intermediate shielding effect of ca. 8 ppm.…”

“…The quantities used in the above procedure, and spectral and analytical data are given below. [17] . …”

Efficient Solid Acid Catalyst Containing Lewis and Brønsted Acid Sites for the Production of Furfurals

“…Among chiral P–H species, ( R P )‐(–)‐menthyl phenylphosphinate ( 1a ) is very commonly used due to the ease with which various groups such as alkyl, vinyl or aryl can be effectively introduced onto the chiral phosphorus atom. Recently we reported the addition of 1a to C=O bonds to form P‐stereogenic α‐hydroxy phosphinates 5a,5b. Also, optically pure 1a was used as precursor of P‐stereogenic secondary phosphine oxides,5c or directly as a ligand for asymmetric hydrogenation 6…”

Straightforward Diastereoselective Synthesis of P-Chirogenic (1R)-1,8,8-Trimethyl-2,4-diaza-3-phosphabicyclo[3.2.1]octane 3-Oxides: Application as Chiral NMR Solvating Agents

“…α-hydroxyl phosphinates [28]. Finally, it was possible to show that the new compounds 16 and 18 can be applied as chiral-solvating agents.…”