Hexamethylphosphorus triamide HMPT

The lrialkyl(trifluorovmyl)slannanes were used in the Pd(0)-catalyzed coupling reaction of aryl halides [77] (equation 12). The product yield increased with the solvent type in the order hexamethylphosphorus triamide (HMPT) DMF > dimethyl sulfoxide (DMSO) > tetrahydrofuran (THF) > CgHg > C2H4CI2. 

The reaction of m-3,5-di(isopropoxycarbonyl)-l,2-dithiolane 113 in dichloromethane with hexamethylphosphorus triamide (HMPT), added over a period of 12 h at room temperature, led to the formation of tram-2,4-di(isopropoxy-carbonyllthietanc 114 in 27% yield (Equation 33) <2000J(P1)1595>. 

Methylcopper is less reactive than lithium dimethylcopper towards acid halides (295), but the yield of methyl ketones can be increased by performing the reaction in hexamethylphosphorus triamide (HMPT) or CHgCN (224). 

Alternative methods for preparing solvated alkali-metal graphites include either secondary solvation of the binary compounds or reduction of graphite by solutions of the alkali metal in electron-solvating media such as hexamethylphosphorus triamide (HMPT) or polycyclic aromatic systems in ethers , leading, e.g., to HMPT- or ether-solvated compounds. 

In the conversion of 66 to 67, we saw that HMPA was used as an additive. Another useful ingredient in many alkylation reactions is hexamethylphosphorus triamide [HMPT, (Me2N)3P], which coordinates with the enolate anion, diminishing the aggregate state and increasing reactivity. This additive also enhances the polarity of the solvent and thereby enhances the facility of the Sn2 alkylation step (sec. 2.7.A.i). The use of an additive such as HMPA or HMPT is very common when the enolate anion reacts slowly and/or the halide is relatively unreactive. Other acid derivatives such as lactones can react with LDA to give an enolate anion, which then reacts with alkyl halides in the usual manner. 

Only moderate variations in kinetic ElZ) ratios are observed except for LHDS, which favored the thermodynamically more stable (Z) enolate. The sterically demanding LTMP favored formation of the kinetic E enolate.22 An equilibration process is clearly occurring, possibly by an aldol addition — retro-aldol process that was suggested by Rathke and co-workers (via 26). The aldol condensation will be discussed in Section 9.4.A. Addition of HMPT (hexamethylphosphorus triamide) destabilizes and deaggregates aldolate 26, promoting equilibration. 

---