Solvent-free reactions Arbuzov

During the synthesis of a group of potential threonine synthase inhibitors, Zervosen studied the synthesis of allylic phosphonates through an Arbuzov-type reaction between allylic bromides and trialkyIphosphites (Scheme 4.48) [100]. Trimethylphosphite was nsed as a representative phosphorus nucleophile in this chemistry. Similar to many of the Arbuzov-type reactions, the chemistry was operationally simple and proceeded under solvent-free conditions. Although the temperature of this process was lower than several of the systems described previously, there are still many substrates that will not survive heating to 100 °C for 8h. 

As stated previously, arylhalides do not typically participate in Arbuzov-type chemistry due to their sluggish behavior in nucleophilic substitution reactions. Typically, metal salts are added to promote the reaction. However, suitably activated systems are known to participate in SNAr reactions using phosphorus nucleophiles. To this end, the pyrazinones have been phosphorylated through a metal-free Arbuzov reaction (Scheme 4.213) [352]. This approach to the functionalization of these heterocycles was attractive since it is operationally straightforward and was successful under solvent-free conditions. A focused microwave... 

Qu and Guo reported that specific positions on purine rings would undergo an Arbuzov-type reaction under solvent-free conditions using a focused microwave reactor (Scheme 4.214) [353]. This chemistry was tolerant of a range of groups at the N9 position... 

One example of a miCTOwave-assisted version of the nickel-catalyzed Arbuzov reaction was operationally trivial and simply involved irradiating the reagents under solvent-free conditions to generate the arylphosphonates (Scheme 4.218) [365]. The isolated yields of the products were good, and a number of number of fuctionalized compounds were screened. 

Microwave-assisted Arbuzov rearrangement under solvent-free condition was found to be an efficient method for the preparation of dialkyl alkylphosphonates of alkyl halides (Kaboudin and Balakrishna, 2001). This method is an easy, rapid, and high-yielding reaction for the Arbuzov rearrangement. 

Shingare and co-workers have presented for the first time a successful implementation of ultrasound irradiation for the rapid synthesis of a-hydroxy phosphonates (521) and a-amino phosphonates (525) under solvent-free conditions from triethyl phosphite (524), aromatic aldehydes (523) and amines (522) using camphor sulfonic acid (CSA) (Scheme 130). One-pot, three-component Kabachnik-Fields synthesis of a-aminophos-phonates (529) from carbonyl compounds (526), primary amines (527), and dibenzyl/dimethyl/diethyl substituted phosphites (528) has been carried out in high yields, using H-beta zeolite as a reusable catalyst (Scheme 131). Zhang and co-workers have developed the nickel-catalysed Arbuzov type phosphonylation to afford phenyl substituted phosphonates (532) in the reaction of aryl triflates (530) with triethyl phosphite (531), in which KBr, as an additive, promoted the Sn2 catalytic step (Scheme 132). ... 

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