Hexamethyl-phosphoric amide

Dimethoxy-l-indanone l-Benzyl-4-piperidinecarboaldehyde Hexamethyl-phosphoric amide... 

The stereoelectronic effect of the RO-group is less pronounced, when bulkier electrophiles are employed (Table 3, entries 23,27,28), but is increased when the well solvating agent hexamethyl phosphorous amide (HMPA) is used as an additive 61,68). On the other hand, if one performs the deprotonation/alkylation sequence in the unpolar solvent pentane, a complete reversal of the stereochemical outcome provides the coproduct in excess (Eq. 35)61 Now a coordination of the lithium cation to the siloxy function might favour structures like 109 (or its oligomers) and cause predominant formation of cO-cyclopropanes. 

Fig. 1. Linear correlation between NMR chemical shifts at infinite dilution of CF3I in various electron pair donor solvents and donicity (DN), referred to CCI3F as external reference. NB, nitrobenzene BN, benzonitrile AN, acetonitrile PDC, propanediol-1, 2-carbonate THF, tetrahydrofuran DMF, dimethylformamide EC, ethylene carbonate TMP, trimethyl phosphate DMA, N,N-dimethylacetamide DMSO, dimethylsulfoxide HMPA, hexamethyl-phosphoric amide.

Stiixe and coworkers (90—93) have condensed appropriately substituted quinones with amino-phenols to yield isolable, single-stranded intermediates which may be converted to ladder structures by treatment at higher temperature. Alternatively, the reaction may be carried out at high temperature in a polar, aprotic solvent such as hexamethyl phosphor-amide (HMP) to 3deld the ladder poljmer directly. 

I Aliphatic ethers, nethvl t-butyl ether, tetramethylguanidine, hexamethyl phosphoric acid amide (trialkyleuaines)... 

Further improvements in dehalogenation selectivity and yields can be achieved by using dipolar aprotic solvents. Dimethylformamide has mostly been used for this purpose,18,56,84 97 although dimethyl sulfoxide,98,99 especially when combined with sonication at room temperature (vide infra), deserves attention in particular cases.100,101 Other polar and dipolar aprotic solvents have also been used, namely, acetone,4 butan-2-one,4 acetonitrile,102 acetic anhydride,103104 ethyl acetate,61 tetrahydrothiophene 1,1-dioxide (sulfolane)105 and hexamethyl-phosphoric triamide,106 but no details were reported on their advantages over dimelhylform-amide or dimethyl sulfoxide. Better performance of dipolar aprotic solvents, such as dimethyl-formamide, over other solvents has been demonstrated in the recent comparison of the dehalogenation of 4,5-dichloro-4,5,5-trifluoropentan-l-ol (4) with zinc in various solvents.90... 

Allyl bromide Hexamethyl phosphoric acid amide... 

Hexamethyl phosphoric triamide l-Chloro-4-acetoxy-2-methyl-2-butene Sodium amide... 

Amide hexamethyl-Phosphoric triamide C3Hi,N30P 680-31-9 144 192 —... 

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