The Synthesis of Dialkyl α-Halogenated Methylphosphonates

Abstract

Mono and dichlorophenols also used as quenching agent ** 4-Methylphenol also used as quenching agent

Recent Advances in H-Phosphonate Chemistry. Part 2. Synthesis of C-Phosphonate Derivatives

“…Transition metal-catalyzed formation of the P-C bond is an important method for preparing organophosphorus compounds [16,19,87], thus enabling the synthesis of C(sp 2 )-P derivatives which are not accessible by the Michaelis-Arbuzov [9,10] or Michaelis-Becker [11,12] reactions. Cross couplings promoted by palladium are stereospecific and occur with retention of configuration at the stereogenic phosphorus center [88][89][90].…”

“…For the formation of the P-C(sp 3 ) bond, the most common approaches are still those involving the Michaelis-Arbuzov [9,10] and the Michaelis-Becker reactions [11,12], or the addition to a carbonyl group [13,14]. However, in recent decades, the transition metal mediated P-C bond formation strategy has started to become widely used, especially in the synthesis of P-C(sp 2 ) derivatives [5,[15][16][17][18].…”

Fluorinated Organozinc Reagents

“…The α-fluorophosphonate moiety has previously been introduced utilizing thermally unstable organolithium reagents 166,167 and fluorinating agents such as DAST 168 . (EtO) 2 P(O)CFHZnBr is thermally stable, scalable and avoids the use of expensive and hazardous fluorination reagents.…”

The Usefulness of Phosphorus Compounds in Alkyne Synthesis

“…Several dialkyl a-halogenated methylphosphonates containing one, two or three halogen atoms, essentially chlorine, bromine and iodine are known. 233 They owe their synthetic utility to their use in the preparation of mono-or dihaloalkenes which are masked alkynes. The facile formation of a carbanion in the a-position to the phosphoryl group coupled to a geminal disubstitution operation of the carbonyl group (Horner-Wadsworth-Emmons reaction) results in the production of mono-or dihaloalkenes able to provide access to internal or terminal alkynes by 1,2-, or 1,1-elimination reactions.…”

“…This route involves the intermediacy of the chloromethylphosphonyl dichloride (67) prepared in up to 67% yield by reacting phosphorus trichloride with formaldehyde at 250 °C. 233,[261][262][263][264][265][266] Further treatment of 67 with anhydrous ethanol produces diethyl chloromethylphosphonate (68) (Scheme 32). 233…”