Hexamethylphosphoric Triamide

Superbase‐Assisted Selective Synthesis of Triarylphosphines from Aryl Halides and Red Phosphorus: Three Consecutive Different SNAr Reactions in One Pot

“…As seen from Table 1, the major factors which influence the triarylphosphines yield are the nature of polar complexing solvent (L) as a ligand of a superbase system (KOH/L) and the structure of aryl halides, mainly the nature of halogen. The best yields of triphenyl-(2a), tritolyl-(2b, 2c), and trinaphthylphosphines (2f, 2g), which span 51-74 % were attained when the reaction was conducted in the KOH/NMP superbase system with corresponding aryl fluorides (entries 2, 17,20,26,30). The close results for the same aryl fluorides were obtained when the reaction was implemented in the KOH/HMPA superbase system, the yield ranging 54-70 % (entries 5, 18,21,27,31).…”

“…The close results for the same aryl fluorides were obtained when the reaction was implemented in the KOH/HMPA superbase system, the yield ranging 54-70 % (entries 5, 18,21,27,31). In view of adverse physiological properties of HMPA as a solvent, [26] the KOH/NMP should be considered as a system of choice. It is worthwhile to note that in the KOH/HMPA system the most significant exothermic effect (132-180°C) have been observed.…”

Anionic Diels–Alder Chemistry of Cyclic Sodium Dien-1-olates Delivering Highly Stereoselective and Functionalized Polycyclic Adducts

“…As seen in entries 1–3, all tested reactions using a strong, medium or weak lithium base in a less polar solvent THF turned out to be fruitless at either ambient or elevated temperature. To further activate the lithium–enolate ion pair, solvation of lithium cation by HMPA in THF (V/V = 1/4) was then examined; however, reactions resulted in a complex unidentified mixture as observed on TLC (entry 4). Interestingly, when lithium carbonate was applied in the more polar solvent DMF at higher temperature (entry 5, 100 °C), products 9 and 10 were obtained in 70% and 15%, respectively, of which the relative configuration is unambiguously determined by a single-crystal X-ray analysis…”

Remote 1,5-Stereoselectivity Control by an N-Ligand Switch in the Pd(0)/InI-Promoted Reactions of 4-Ethynyl-β-lactams with Aldehydes

“…Initially, the formation of propargylindium from readily accessible racemic N -Ts-4-ethynylazetidin-2-one 1 and its subsequent addition to benzaldehyde under our two previously reported conditions was attempted. , The application of 2 equiv of InI and 5 mol % of Pd­(PPh 3 ) 4 in a 3:1 THF/HMPA mixture at 25 °C gave exclusively 2,5- syn -allenediol 2 in high 79% total yield and with excellent central-to-axial chirality transfer. However, an inseparable mixture of two C6-epimers 2a and 2b (43:57 d.r.)…”

“…2,6- anti -selectivity (Table , entry 3). Further experiments using modified THF/HMPA ratio mixtures and attempts of replacing THF and/or toxic HMPA with other polar cosolvents (DMPU, DMI, DMF, NMP, and DMSO) failed since, in all cases, a noticeable drop in yield and/or stereoselectivity was observed. On the other hand, replacing N -MI with other amines (NEt 3 , DIPEA, quinuclidine, pyridine, 2,6-lutidine, quinoline, isoquinoline, N -methylmorpholine) led to interesting results.…”