Lucien Gouin

Addition de l'acide thiocyanique aux acetyleniques a l'aide de Hg(II)-I : Addition du groupement (SCN)- en presence d'un acide fort

Resume Mercury(II) thiocyanate Hg(SCN) 2 catalyses thiocyanic acid HSCN addition to unactivated acetylenic compounds R 1 -CC-R 2 . Bonding of the SCN moiety to carbon occurs through sulphur or nitrogen depending upon the influence of R 1 and R 2 ; vinyl thiocyanates NCS-C(R 1 )CH 2 are obtained specifically from terminal acetylenic compounds but some symmetrically disubstituted alkynes may afford vinyl isothiocyanates SCN-C(R 1 )CH–R 2 (R 1 R 2 Et, n-Bu). A simple preparation of tet- raphenylphosphonium hydrogen dithiocyanate Ph 4 P+[H(SCN) 2 ] - is reported.

L'addition des organomagnesiens aliphatiques satures sur les triples liaisons disubstituees non conjuguees: IV. Influence d'un groupement fonctionnel thioether en α de la triple liaison. Action catalytique du cuivre

Abstract The addition reaction of ethylmagnesium bromide to the triple bond of the compounds of general formula EtSCH 2 C CCH 2 Y (where Y is the basic group OH, OR, NR 2 , or SEt) is very weakly activated by the thioether group. Catalysis by magnesium impurities may be involved. With 1-ethylthio-4-dialkylamino-2-butynes (Y NR 2 ), ( E ) trisubstituted ethylenic compounds are selectively obtained. The reaction more readily occurs after the addition of cuprous chloride to the Grignard solution, and then its stereoselecitvity may be reversed.

Thiocyanatomercuration des acetyleniques. Synthese de derives β-(iso)thiocyanatoalcenyl mercuriques, d'α-halo β-thiocyanato alcenes et de thiocyanato-1 alcynes-1

Abstract In the presence of (SCN) − mercuric chloride HgCl 2 adds to acetylenic compounds R 1 CCR 2 affording in most cases α-chloromercuri-β-thiocyanatoalkenes R 1 C(SCN)C(R 2 )HgCl and if R 1 = R 2 = Et or n-Bu isothiocyanates R 1 C(NCS)C(R 2 )HgCl. The action of halogens or thio compounds affords α-halo-β-thiocyanatoalkenes. Most of the reported reactions are regio- and stereo-specific, in particular both RC(SCN)CHBr and RCBrCHSCN may be regiospecifically obtained from 1-alkynes RCCH. The synthesis of 1-thiocyanato-1-alkynes is also reported.

Addition de l'acide thiocyanique aux acétyléniques à l'aide de Hg(II). II: obtention d'isothiocyanates vinyliques par mercuration-protodemercuration

Abstract Thiocyanic acid HSCN is added to some acetylenic compounds R 1 -C& 2 through a two-step one-pot procedure wich involves, first, the generation in CH 2 Cl 2 of β-thiocyanato and/or β-isothiocyanato alkenyl mercuric coupounds R 1 -C (SCN)=CR 2 -Hg- by addition of mercury (II) thiocyanate Hg(SCN) 2 to R 1 -C& 2 then the substitution of mercury by hydrogen through acidic treatment. In proper conditions of stoechiometry and reaction time the process is tharmodynamically controlled and thus allows to obtain vinyl isothiocyanates R 1 -C(-NCS)CHR 2 even when the isomeric vinyl thiocyanates are kinetically favoured. Preparation of 3,3- dimethyl 2-isothiocyanato 1-thiocyanato 1-butene is also reported.

Nuclear magnetic resonance studies of the difluoride ion. Part 3.—Ammonium and substituted ammonium difluorides

The 19F free induction decays from the difluoride ion in the ammonium, phenylamine, 2- and 4-methylphenylamine salts have been fitted theoretically by a Fourier transform of the lineshape function. In all four compounds, the best fit is obtained for a centred difluoride ion with F … F = 2.34 A(motionally-corrected value of 2.28 A); in the phenylamine and methylphenylamine difluorides the maximum departure of the proton from the centred position is 0.05 A.

Nuclear magnetic resonance and quadrupole resonance studies of triethylamine dihydrochloride

35 Cl quadrupole resonance and 1H magnetic resonance studies of the adduct NEt3· 2HCl show its structure to be [NEt3H]+HCl–2 in the crystalline solid and in solutions in chloroform. In both phases, the dichloride ion appears to be asymmetric, so that the limiting proton chemical shift in solution is close to 10 p.p.m., compared to values of 14 p.p.m. for the symmetric ion. The factor which stabilizes the asymmetric configuration is believed to be hydrogen-bonding to the cation of the type [NEt3H]+…ClHCl–. It is proposed that the close approach of any positively-charged species along directions close to that of the Cl…Cl axis will stabilize the asymmetric ion; otherwise the ion will tend to be symmetrical, or at least will appear to be so within the time-scale of these experiments. The potential well for proton motion in the dichloride ion appears therefore to be relatively broad, unlike that in HF–2.

Nuclear magnetic resonance studies of the difluoride ion. Part 4.—19F and 1H high-resolution spectra of “amine.n HF” complexes

The 1H and 19F high-resolution magnetic resonance spectra of solutions of amine adducts of the form “amine. n HF”, with n= 1, 1.5, 2 and amine = NEt3, NBun2H, NBun3, C6H5NH2, and p-MeC6H4NH2 have been studied both at room temperature and –80°C. Spectra from both F– and HF–2 ions have been detected, the parameters for the latter showing only small differences from those previously observed in solutions of [Bun4N]+HF–2. It seems probable that the difluoride ion is little distorted from a centred configuration in all such solutions.

Ionic additions to unsaturated systems. Part 2. Triethylammonium hydrogendichloride as reagent in the addition of hydrogen chloride to alkynes

Addition of hydrogen chloride to the carbon–carbon triple bond may easily be performed by means of triethyl-ammonium hydrogendichloride (Et3NH+HCl2–): an equimolar mixture of this reagent with an alkyne, either neat or dissolved in an aprotic medium, affords the 1 : 1 addition product in high yield, without a catalyst. This method has been applied to dimethyl but-2-ynedioate, 3-chloropropyne, phenylacetylene, 1-phenylpropyne, and 3,3-dimethyl-1-phenylbut-1-yne. The reaction proceeds essentially through anti-addition of hydrogen chloride; predominant but non-exclusive syn-addition is only observed with 3,3-dimethyl-1-phenylbut-1-yne. The results are discussed in terms of the ambivalent character of the HCl2– ion, which acts both as a precursor of hydrogen chloride and as a powerful nucleophilic reagent, and prevents to some extent the formation of vinyl cation intermediates that normally are easily generated by protonation of alkylphenylacetylenes; the results also provide new evidence of the importance of the nucleophilic character of the species involved in the C–Cl bond formation in controlling the stereochemical course of the electrophilic addition of hydrogen chloride to alkynes.