Vinylamines

Unlike the other stmctural isomers of C2H N, /V-methylenemethylamine (33,34), ethylideneimine (35), and vinylamine [593-67-9] (36,37) and the analogous phosphoms compound, phosphirane (38), ethyleneimine is stable at room temperature provided CO2 is excluded from the air (39). Unexpectedly, ethyleneimine has the highest calculated relative heat of formation of the C2H N isomers (40). Relative calculated heats of formation are ethylideneimine. 

Dihydroazoles can exist in at least three forms (cf. Section 4.01.1.3), which in the absence of substituents are tautomeric with each other. The forms in which there is no hydrogen on at least one ring nitrogen normally predominate because imines are generally more stable than vinylamines in aliphatic chemistry. Thus for dihydropyrazoles the stability order is A" (hydrazone) (288) > A (azo) (289) >A (enehydrazine) (290). 

Nitrone (530) exists in thermal equilibrium with vinylamine (531) and isoxazolidine (532), with (532) (a dimer of 530 and 531) being predominant. The equilibrium in DMSO was studied by and NMR spectra (80TL3447). 

The above considerations presuppose that two important conditions are fulfilled. First the nitrogen must be tertiary, as primary and secondary vinylamines are generally more stable in the imine form (5). Only in the case of enamino ketones and esters are the enamine more stable than the imine forms (7). Secondly, the atoms comprising the tt system must be able... 

Electrochemical fluorination of cyclic 2-(dialkylamino)-propionic acids provides a general route to optically active perfluoro-(2-cycIic(dialkyl-amino)-propionic acids [91 JFC(52) 133], which are a source of perfluorinated vinylamines (88CL1887). 

Vinyl cations also have been proposed as intermediates in the deamination of vinylamine, 135(113). When diphenylvinylamine,, 135, was dissolved in boiling benzene and isoamylnitrite was added, diphenylacetylene formed in 50-85% yield in 3-5 h. The sequence of reactions shown in Scheme IX has been proposed as a possible route to the observed product (113). 

The condensation of NH3 with acetylene can give rise to vinylamine, which is probably an intermediate (together with ethyUdeneimine) in the formation of acetonitrile and other condensation products (Scheme 4-7). 

In contrast, the reaction of morpholine with phenylacetylene is less regioselective. Two products are formed, arising from two vinylamine intermediates (Scheme 4-12) [257]. 

PI1NH2 reacts with alkynes in the presence of HgO-BF, to give N-phenylalkylide-neamines arising from the isomerization of the initially formed vinylamines (Eq. 4.63) [258]. 

PhNHEt and 1-heptyne afford a N-vinylamine as a stable Markovnikov hydroamination product (Eq. 4.64) [258]. 

The fluid loss control of aqueous, clay-based drilling mud compositions is enhanced by the addition of a hydrolyzed copolymer of acrylamide and an N-vinylamide [402], The copolymer, which is effective over a broad range of molecular weights, contains at least 5 mole-percent of the N-vinylamide units, which are hydrolyzed to N-vinylamine units. The copolymers can be made from various ratios of N-vinylamide and acrylamide by using common radical-initiated chain growth polymerization techniques. 

T. W. Lai and B. R. Vijayendran. Cement composition for oil well drilling holes containing high molecular weight poly(vinylamines). Patent EP 331045, 1989. 

When secondary amines are heated with ketones or aldehydes in the presence of an acidic catalyst, a related reaction occurs, and the product is a substituted vinylamine or enamine. 

Spange, S., Meyer, T., Voigt, I., Eschner, M., Estel, K., Pleul, D. and Simon, F. Poly(Vinyl-formamide-co-Vinylamine)/Inorganic Oxid Hybrid Materials. Vol. 165, pp. 43-78. 

Diphenylcyclopropene thione also reacts with Schiff bases 379 via the tautomeric vinylamine form to give betaines 380, which tautomerize to the bicyclic thio amides 3 /247 ... 

Likewise, Schiff bases of type 379 react with triafulvenes again (see p. 75) via the tautomeric vinylamine form to give products of C—C-insertion 253. In the presence of a COOR group at triafulvene C4, the cross-conjugated system 536 undergoes facile cyclization to 2-pyridones 537 by loss of alcohol. 

A particularly dramatic effect of hyperconjugation on the form of the ethylenic double bond NBOs is shown in Fig. 3.50. This figure depicts one of the two equivalent C=C bond and antibond NBOs of vinylamine, twisted slightly out of coplanarity with the nitrogen lone pair with dihedral

[Pg.219]

Figure 3.54 shows the form of two singly occupied spin-NBOs in the vinylamine triplet excited state the 7tCN 1 half-bond of the (3 spin set (Fig. 3.54(a)) and the terminal nc radical orbital of the a spin set (Fig. 3.54(b)). Neither of these orbitals has a true counterpart in the MOs or NBOs of the ground-state molecule. These results emphasize that hyperconjugative reorganization is a strong feature of the excited-state orbitals, and the oversimplified HOMO-LUMO (Koopmans-like)... 

Figure 3.54 Singly occupied spin-NBOs of the lowest triplet 7t 7t+ excited state of vinylamine (X = NH2) (a) The 7TCn half-bond, (3 spin and (b) the ncf radical orbital of the terminal C atom, a spin.

The parameterization of MM2 and MM3 for enamines and aniline derivatives was based on the experimental and ab initio results of vinylamine, /V-methylvinylamine, aniline, N-methylaniline and iV.iV-dirnclhylanilinc. A complete list of parameters for both force fields is provided in Reference 44. 

---