Fluoride-Mediated Dephosphonylation of α-Diazo-β-carbonyl Phosphonates
The possibility of fluoride-mediated selective dephosphonylation of α-diazo-β-carbonyl phosphonates such as the Ohira-Bestmann reagent has been proposed and executed. The resulting α-diazocarbonyl intermediates undergo a (3 + 2)-cycloaddition at room temperature with conjugated olefins and benzynes. Interestingly, under the current conditions, the resulting cycloaddition products underwent either N-acylation (with excess α-diazo-β-carbonyl phosphonates) or Michael addition (with conjugated olefins).
Phatake, Ravindra S.,Mullapudi, Venkannababu,Wakchaure, Vivek C.,Ramana, Chepuri V.
supporting information
p. 372 - 375
(2017/04/21)
Fluoride ion in phosphoryl transfer. A catalyst or an inhibitor?
Fluoride ions have been found to affect hydrolysis of aryl phosphates by more than one mechanism.For substrates with a leaving group like the anions of p-nitrophenol or the N-methyl-8-hydroxyquinolinium ion, F- accelerated the rate via fast formation and decay of the phosphorofluoridate intermediate.For a case when the reaction was autocatalysed (protonation of the leaving group by the acidic product), fluoride ion acted as a net inhibitor due to the elimination of acidic catalysis.The same effect was observed for the hydrolysis of dimethyl phosphorofluoridate.LiF was found to be much less effective in nucleophilic catalysis than other fluoride salts.
Mentz, Marian,Modro, Tomasz A.
p. 2223 - 2226
(2007/10/03)
TRANSFORMATION OF ORGANOPHOSPHORUS S-TRIFLUOROMETHYLTHIOATES RR'P(O)SCF3 INTO FLUORIDES RR'P(O)F. STEREOCHEMICAL ASPECTS OF THIOCARBONYL FLUORIDE EXTRUSION
The stereochemical course of the thermal or by nucleophiles catalyzed extrusion reaction of thiocarbonyl fluoride from two diastereomeric (6) and optically active (10) organophosphorus S-trifluoromethylthioates has been investigated.To explain the observed retention of configuration at phosphorus in fluoridates 7 formed in the thermal reactions, a four center transition state for such reactions has been proposed.The lack of the stereoselectivity in the catalyzed reactions of 6, and the observed racemization of the final product 11 are briefly discussed.
Lopusinski, Andrezej
p. 383 - 390
(2007/10/02)
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