Abstract
LiTMP metalated dimethyl N-Boc-phosphoramidates derived from 1-phenylethylamine and 1,2,3,4-tetrahydronaphthalen-1-ylamine highly selectively at the CH3O group to generate short-lived oxymethyllithiums. These isomerized to diastereomeric hydroxymethylphosphonamidates (phosphate–phosphonate rearrangement). However, s-BuLi converted the dimethyl N-Boc-phosphoramidate derived from 1-phenylethylamine to the N-Boc α-aminophosphonate preferentially. Only s-BuLi deprotonated dimethyl hydroxymethylphosphonamidates at the benzylic position and dimethyl N-Boc α-aminophosphonates at the CH3O group to induce phosphonate–phosphinate rearrangements. In the former case, the migration of the phosphorus substituent from the nitrogen to the carbon atom followed a retentive course with some racemization because of the involvement of a benzyllithium as an intermediate.
Highlights
Phosphonates playing a very minor role in biological systems than phosphates are accessible by a variety of methods
We have shown that phosphoric acid derivates, phosphates, S-alkyl thiophosphates, and phosphoramidates can be base-induced isomerized at low temperatures to αhydroxy,1,2 α-mercapto,3 and α-aminophosphonates,[4] respectively (Scheme 1)
Various Phosphate−Phosphonate Rearrangements metalated by strong lithium bases to form presumably shortlived, dipole-stabilized α-heteroatom substituted alkyllthiums 2a−c, which undergo a migration of the dialkoxyphosphinyl substituent from the heteroatom X (= O, S, NR) to the carbon atom
Summary
Phosphonates playing a very minor role in biological systems than phosphates are accessible by a variety of methods. We have shown that phosphoric acid derivates, phosphates, S-alkyl thiophosphates, and phosphoramidates can be base-induced isomerized at low temperatures to αhydroxy-,1,2 α-mercapto-,3 and α-aminophosphonates,[4] respectively (Scheme 1). Various Phosphate−Phosphonate Rearrangements metalated by strong lithium bases to form presumably shortlived, dipole-stabilized α-heteroatom substituted alkyllthiums 2a−c, which undergo a migration of the dialkoxyphosphinyl substituent from the heteroatom X (= O, S, NR) to the carbon atom. The phosphate− phosphonate rearrangements follow a retentive course[2−4] at the carbon atom, even if it is a benzylic position except for X = S. Metalation at the benzylic position of the lithiated α-mercaptobenzylphosphonate of unknown configuration followed by protonation on work up gives a racemic product.[3] The stereochemistry at the phosphorus atom remains to be unraveled.
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