Substituted vinylamines

The nucleophilic properties of the double bond in vinylamines substituted on nitrogen by a strong electron-withdrawing group (nitro, carbonyl, sufonyl etc.) are preserved and they undergo addition of dichlorocarbene to give the corresponding 1,1-dichlorocyclopropanes. 

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. 

Newman projections along the N—C1 bond showing the six conformations, 116 to 121, of vinylamine (115) whose total energies in various basis sets have been collected in Table 9. (O denotes C1.) Values for substituted vinyl amines refer to the same type of the five conformations 116, 117 and 119 to 121. 

TABLE 10. Basis set dependence of calculated heavy atom parameters of a-substituted vinylamines 2-aminopropene (125), 1-amino-1-fluoroethene (126) and 1-amino-1-hydroxyethene (136). Distances in A and angles in deg... 

The calculated gas-phase barriers to internal rotation225 around the C1=C2 bond decrease by 56.60, 47.01 and 41.59 kcal mol-1 in the sequence CN > CHO > N02, which parallels the increase in electron-attracting power of these three substituents. The transition state of this rotation is best described by a zwitterionic rotated configuration of the type indicated in 98b to 98d. The barrier to internal rotation around the C1—N1 bond varies in the reversed order from 21.82, 17.56 to 12.77 kcal mol-1 for 129, 130, and 131, respectively. Both trends are consistent with the variations of the electron-acceptor properties of the substituents which decrease in the sequence N02 > CHO > CN. The rotational barriers of / -CH3 and / -F substituted vinylamines 127 and 128 are calculated in the 6-31G basis set to be much lower 3.13 kcal mol-1 for the E-CH3 substituent 127a, (in parentheses, the value for the higher barrier to type 120 4.64 kcal mol-x), 2.80 (4.64 kcal mol-1) for Z-CH3 (127b) for E-F 0.33 (2.89 kcal -mol-1), and for 128b a reversal of the two barriers. That barrier to type 121 is now 4.55 kcal mol-1, and that to 120 is 3.89 kcal mol-1. 

The interaction of ethene with planar ammonia leads to the MOs of coplanar vinylamine (115) in the form 116. The HOMO n2 (with N lone-pair and C=C -character) is now at —0.298 hartree ( —8.10eV) and the splitting between nx and n2 has a maximum value of 5.20 eV. On torsion of the planar amino group to the perpendicular conformation 119 this splitting decreases to 0.18 eV. All three values differ strongly from experimental data presented in Table 18, but they refer to variously substituted tertiary enamines, so that from calculations of 115 we only may detect trends. 

Aryl-substituted amino alcohols fail to undergo this reaction but instead are dehydrated to vinylamines. 

Poly(methoxymethylstyrene) and co-polymers from (2,2-disubstituted 1,.5-dioxolan-4-yl)methoxymethylstyrene crosslink readily under u.v. light (Scheme 17). Here both the 1,3-dioxolane and benzyl methyl ether structures participate in the crosslinking. o-Nitrobenzyl cholate esters have been used as effective photosensitizers in resists," as have poly-(N-vinylamine) and methacrylate co-polymers with substituted cinnamic or cinnamylidene groups. 

Deamination of a-substituted- 3-2-(5-nitrofuryl)vinylamines 43 (R = substituted Ph, 1-naphthyl, 2-furyl) with isoamyl nitrite in dioxane at 80 °C gives p-2-(5-nitro-furyl)acetylenes 44 in good yields . 

The main deficiencies with the preceding approaches are that only arylene-amines give good yields (and there are other routes to 5-arylimidazolcs), and since unsubstituted vinylamines (R = H Scheme 4.3.3) are not available this means that 4- and 5-unsubstituted imidazoles are not accessible. An alternative route involving silyl enol ethers (6) has been reported to overcome these deficiencies (Scheme 4.3.4). Silyl enol ethers can be made either by treating a ketone with chlorotrimethylsilane and triethylamine in DMF solution, or by sequential reactions of the ketone with LDA and chlorotrimethylsilane in 1,2-dimethoxyethane. This normally gives a mixture in which the less highly substituted enol ether is the major product (enolate formation is kinetically controlled) [25], When (6) is heated with an At-chloroamidine for 12-24h in chloroform solution in the presence of an equimolar amount of dry pyridine 1,2-disubstituted (5) (R = H) or 1,2,5-trisubstituted (5) imidazoles are... 

The cycloaddition of l-methoxy-3-trimethylsilyoxy-1,3-butadiene with 3-methyl-1,2-benziso-thiazole 1,1-dioxide (107) (R = Me) affords the pyridone (108) <84H(22)67l>. An improved synthesis of 1,2-benzisothiazole 1,1-dioxide has led to the preparation of the benzothiazepine (109) (R = H) by cycloaddition of the ynamine followed by ring expansion <83CC520>. Addition of yV,7V-diaikylprop-l-ynamines to 3-substituted 1,2-benzisothiazole 1,1-dioxide (107) (R = SMe, SPh, SePh) gives mainly the imine-vinylamine (110) with only small amounts of the benzothiazepine (109) <85CC845>. 

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