Functionalization of α-hydroxyphosphonates as a convenient route toN-tosyl-α-aminophosphonates

Abstract

Direct conversion of the a-hydroxyl group by para-toluenesulfonamide to yield a-(N-tosyl)aminophosphonates is reported. a-Aminophosphonates 23a,b-37a,b were obtained from the corresponding a-hydroxyphosphonates 6a,b-21a,b in the presence of K 2 CO 3 , via the retro-Abramov reaction of the appropriate aldehydes, 1-5. The subsequent formation of imines with simultaneous addition of diethyl phosphite provided access to the a-sulfonamide phosphonates 23a,b-37a,b with better diastereoselectivity than in the case of the Pudovik reaction. The mechanism for this transformation is proposed herein. When Cbz N-protected aziridine 9a,b and phenylalanine analogue 12a,b were exploited, intramolecular substitution was observed, leading to the corresponding epoxide 38 as the sole product, or oxazolidin-2-one 39 as a minor product. Analogous substitution was not observed in the case of proline 18a,b and serine 21a,b derivatives.

Regioselective Fluorination of α‐Hydroxy‐β‐aminophosphonates by Using PyFluor

“…Preparation of Compounds 13a–13i: α‐Hydroxy‐β‐aminophosphonates 13a – 13i were prepared according to a previously reported procedure. The NMR spectroscopic data for 13a , 13b , and 13d – 13h were in good agreement with that in the literature , …”

“…Figure shows the perspective views of 13c and 13g . The structural data for 13d were recently reported . Two of three compounds (i.e., 13d and 13g ) crystallized in chiral space groups as a single enantiomer (1 R ,2 S ).…”

The typical crystal structures of a few representative α-aryl-α-hydroxyphosphonates

“…In this case, only a minimal amount of acetone and pentane was necessary as the solvent (Keglevich et al, 2017). A convenient functionalization of -hydroxyphosphonates was also reported recently (Cytlak et al, 2018) en route to the synthesis ofaminophosphonates. Several such novel -aminophosphonate crystal structures were also reported (Cytlak et al, 2018).…”

“…A convenient functionalization of -hydroxyphosphonates was also reported recently (Cytlak et al, 2018) en route to the synthesis ofaminophosphonates. Several such novel -aminophosphonate crystal structures were also reported (Cytlak et al, 2018). The structure determination of phosphonates was soon undertaken as their economic value grew.…”

Synthesis ofα‐Hydroxyphosphonates Containing Functionalized 1,2,3‐Triazoles

“…Aiming to determine the best reaction conditions for the reaction, 2‐(4‐phenyl‐1 H ‐1,2,3‐triazol‐1‐yl)benzaldehyde ( 1 a ) and diethyl phosphite ( 2 a ) were chosen as the standard starting materials. Initially, the used reaction conditions were adapted from previous reports, [75–77] in which a solvent‐free mixture of triazole 1 a (0.25 mmol) reacted with 3.0 equiv. of diethyl phosphite ( 2 a ) reacted at 70 °C in an open vessel system.…”