Titanium tetrachloride promoted condensations of amines with carboxamides and similar species

Boron trihalide adducts of 1,1-bis(piperidinyl)ethylene. 13C and 11B nmr studies of a model system for β-carbon donation in enamine adducts

“…We now report 13C and lLB nmr diamines (2). This is well established for protons-studies of boron trihalide coordination of 1,l-bis- 13C nmr parameters of 4 and its boron trihalide tion (2). The few available studies of complexation adducts are given in Table 1-The P-carbon of 1,l-enediamines to simple Lewis acids (boron uncom~lexed 4 absorbs exce~tionall~ far to high trihalides (3) and Group IV tetrahalides (4)) also field for an olefinic carbon, and this can be attribshow that complexation is at the P-carbon site.…”

“…Supporting evidence for our assignments comes from addition of tetramethylammonium iodide to solutions of 4 and BI,. The size of the initially-small -78ppm peak, assigned to 4.B13, is greatly increased relative to both of the lower-field peaks, in accord with reactions such as [2]. (Table 3), makes it unlikely that any further broad resonance signals, such as might arise from D3BBr2+, would be detectable.…”

Urea – boron trihalide adducts. V. Effects of acid strength on restricted rotation in adducts of tetramethylurea and 1,1-bis(dimethylamino)ethylene

“…The proton nmr spectrum consisted of two singlets of relative intensity 6:l at 6 2.54 and 6 3.15 respectively; these chemical shifts showed negligible variation with temperature (-0.06 ppm between -90 "C and +80 "C). Protonation of 2 occurs readily to give 5 (8) having two proton resonances of relative intensity 4:l a t 6 3.33 and 8 2.55; the larger (N-methyl) resonance was barely resolved into a 1:3:3:1 quartet by long-range coupling (0.37 Hz) to the C-methyl protons. Small peaks corresponding to 5 were often present in proton spectra of adducts of 2.…”

“…Compound 2 itself is a reasonably strong base, protonating on the CH2 carbon to give the tetramethylacetamidinium ion 5 (8). Complexation to the boron trihalides is directly analogous.…”

1,3-Dibromo-5,5-dimethylhydantoin as a New Imidazolidine Dehydrogenating Agent: Synthesis of 4,5-Dihydro-1H-imidazolium Salts

“…14,15 Synthesis of 4,5-dihydro-1H-imidazolium salts by dehydrogenation of imidazolidines results a highly attractive method due to the easy preparation of precursor aminals by condensation of aldehydes with properly substituted ethylenediamines. 14,15 Synthesis of 4,5-dihydro-1H-imidazolium salts by dehydrogenation of imidazolidines results a highly attractive method due to the easy preparation of precursor aminals by condensation of aldehydes with properly substituted ethylenediamines.…”