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Herstellung und Reaktionen der valenzpolaromeren Verbindung (4,4‐Dimethyl‐2‐thiazolin‐5‐dimethyliminium)‐2‐thiolat ⇌ (1‐Dimethylthiocarbamoyl‐1‐methyl‐äthyl)‐isothiocyanat aus 3‐Dimethyl‐amino‐2,2‐dimethyl‐2 H ‐azirin und Schwefelkohlenstoff
Author(s) -
Chaloupka Stanislav,
Heimgartner Heinz,
Schmid Hans,
Link Helmut,
Schönholzer Peter,
Bernauer Karl
Publication year - 1976
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19760590733
Subject(s) - chemistry , dimethylamine , azirine , carbon disulfide , medicinal chemistry , sodium borohydride , molecule , organic chemistry , catalysis , ring (chemistry)
Synthesis and reactions of the valence polaromeric compound (4,4‐dimethyl‐2‐thiazoline‐5‐dimethyliminium)‐2‐thiolate ⇌ 1‐dimethylthiocarbamoyl‐1‐methyl‐ethyl isothiocyanate from 3‐dimethylamino‐2,2‐dimethyl‐2 H ‐azirine and carbon disulfide. 3‐Dimethylamino‐2,2‐dimethyl‐2 H ‐azirine ( 1 ) reacts with carbon disulfide to give crystals which have the dipolar structure 3a [(4,4‐dimethyl‐2‐thiazoline‐5‐dimethyliminium)‐2‐thiolate, Scheme 1 ]. In solution, the non‐dipolar (charge‐free) isomeric form 3b (1‐Dimethyl‐thiocarbamoyl‐1‐methyl‐ethyl isothiocyanate) is almost exclusively populated. Reaction products are derived from both forms: Derivatives of 3a are the hydrolysis product 6 , the sodium borohydride reduction product 7 and the methylation products 9 and 10 , respectively ( Scheme 2 ). The isothiocyanate form 3b is responsible for the various reaction products with amines ( Scheme 3 ). One of the reaction products with ammonia, namely 20 , is also obtained by the reaction of 1 with thiocyanic acid. Thermolysis of the azirine/carbon disulfide adduct 3 leads to 2‐dimethylamino‐4,4‐dimethyl‐2‐thiazoline‐5‐thione ( 17 ) in high yield. A possible mechanism is outlined in Scheme 4 . The same compound is also formed by rearrangement of 3 under the catalytic influence of dimethylamine. Its structure has been established by X‐ray crystallography (section 4). Again a rearrangement is involved in the reductive (NaBH 4 ) conversion of 17 to 7 , the direct reduction product of the dipolar species 3a ( Scheme 5 ). The isothiocyanate form 3b is able to react with a second molecule of 3‐dimethylamino‐2,2‐dimethyl‐2 H ‐azirine ( 1 ) to yield compound 25 , which in the crystalline or dissolved state appears to be almost entirely populated by the carbodiimide form with structure 25b ( Scheme 7 ), though all reaction products of 25 (reduction with sodium borohydride, addition of water or hydrogen sulfide, Schemes 7 and 8 ) are derived from the dipolar form 25a , not detectable as such; here again therefore there is a dynamic equilibrium 25a ⇌ 25b . The two forms of adduct 3 , namely 3a and 3b , are obviously very easily interconverted at room temperature and therefore can be considered as valence polaromeric forms (section 5). A classification of the dipolar (zwitterionic) form is given, which allows a comparison of various dipolar species and gives as indication of charge stabilization by delocalization. The versatile reactivity of the 3‐dimethylamino‐2,2‐dimethyl‐2 H ‐azirine/carbon disulfide adduct is demonstrated by the fact that with simple reagents approximately 25 derivatives have been obtained, most of them being new heterocyclic compounds.