62-Imidazolines aromatization

A -Imidazolines, -oxazolines and -thiazolines (291), and their benzo derivatives (292), are very easily aromatized (292 293), and syntheses which might be expected to yield... 

Imidazoline-4-thione, 4,4-diaryl-rearrangement, S, 376 2-Imidazoline-4-thione, 5,5-diaryl-rearrangement, S, 376 2-Imidazoline-4-thione, 5,5-diphenyl-aromatization, 5, 422 2-Imidazoline-5-thione, 4,4-diaryl-rearrangement, 5, 376 2-Imidazoline-5-thione, 5,5-diaryl-rearrangement, S, 376 Imidazolinethiones acylation, S, 424 alkylation, S, 444 C NMR, S, 355... 

Condensation of aromatic methylesters such as methyl 4-methoxybenzoate 351 a or methyl 4-hydroxybenzoate 351b with excess sodium-HMDS 486 in a mixture of THF-l,3-dimethyl-imidazolin-2-one (DMEU) at 185 °C in a closed vessel affords 59 or 93% of 4-hydroxybenzonitrile 298 as well as 26% 352 with smooth cleavage of the aromatic methyl ether in 351a (Scheme 4.47). Methyl indole-3-carboxylate gives hkewise 3-cyanoindole in 81% yield [127] (cf. also ref [92] in section 4.3). 

Interposition of an oxygen atom between the aromatic ring and the imidazoline-bearing side chain leads to a compound reported to show antidepressant activity. Its preparation begins with alkylation of phenol 125 with chloroacetonitrile to afford intermediate 126. Condensation of that nitrile with the... 

The only cationic surfactant (Fig. 23) found in any quantity in the environment is ditallow dimethylammonium chloride (DTDMAC), which is mainly the quaternary ammonium salt distearyldimethylammonium chloride (DSDMAC). The organic chemistry and characterization of cationic surfactants has been reported and reviewed [330 - 332 ]. The different types of cationic surfactants are fatty acid amides [333], amidoamine [334], imidazoline [335], petroleum feed stock derived surfactants [336], nitrile-derived surfactants [337], aromatic and cyclic surfactants [338], non-nitrogen containing compounds [339], polymeric cationic surfactants [340], and amine oxides [341]. 

The electron density induced at the metal center increases in the order C(OR)R < C(NHR)R < C(NHR)2 imidazolidin-2-ylidene imidazolin-2-ylidene. According to these data the difference between diamino-substituted carbenes whether cyclic or acyclic, aromatic or nonaromatic, seems to be quite small. 

A variety of heterocyclic systems containing unsaturated nitrogen can partake in directed aromatic or heteroaromatic lithiations. Pyrazole (II,D), tetrazole (II,G,2), imidazoline (V,B,2), and pyridine (IV,A,4) derivatives were discussed in the sections indicated. In addition, lithio derivatives of 2-oxazoline 178 (76LA183), 4,4-dimethyl-2-oxazoline 179 (790R1 85T837),... 

These aromatic diamidines inhibit IL-1 production and also block IL-6 and TNF. Imidazoline blocks IL-1 and TNF and is less toxic to the cell with an in vitro LD50 1(H. Examples of these compounds are... 

Crysts, mp 141.2° with decompn. Can be prepd by treating a soln of 2-nitramino-A1-imidazo iine in 70% nitric acid with NaNOa. Treating l-nitroso-2-nitramino -AMmidazoline with aromatic amines in acj ethane at 30° gave l-substituted-2-nitramino-A3-imidazolines and... 

The peripheral receptors activated by noradrenaline fall into at least two classes, a-receptors and /3-receptors, which differ in their function and in their response to drugs. The a-receptors cause constriction of blood vessels and compounds used to block them include indoramin (216), prazosin (217) and phentolamine (218). Another imidazoline, tolazoline (2-benzyl-2-imidazoline), is a useful vasodilator but is unsuitable for the treatment of hypertension since it stimulates the heart. Other drugs described as peripheral vasodilators are diazoxide (219), which is related to the thiazide diuretics, hydralazine (220) which also depresses the CNS, hydracarbazine (221) and minoxidil (222). The /3-receptors control the action of adrenaline on the heart (among other effects) and the agents that block them are mostly nonheterocyclic aromatic compounds with aminoethanol or 3-amino-2-hydroxypropoxy side-chains. They have proved effective in the treatment of hypertension. One heterocyclic compound of this class, timolol (223), is in use. 

The enthalpy of formation of CH3N=CHNHCH3 is unknown and all but unprecedented. Indeed, if we exclude such cyclic and already (if only putatively) aromatic species such as adenine and cytosine, the only amidines for which the enthalpies of formation are known are 3,4,5,6-tetrahydropyrimidine [34] and the 2,4,5-triar-ylated imidazolines, amarine [60], anisine [60], and hydrocinnamide [61] from studies over a century old (as cited in [46]). The last species have only been studied as solids, and their antiquity additionally suggests ignoring these values. Accordingly, let us use the first enunciated value and assume thermoneutrality for the reaction ... 

The transesterification with secondary alcohols was also reported by the same group [72], By utilizing l,3-dicydohexyl-imidazolin-2-ylidene (ICy, 11) as catalyst, various alcohols 87 (including aliphatic cyclic and aromatic alcohols) reacted with diverse esters 88 to yield the desired esters 89 (Scheme 9.26). The steric bulk at the a position of the alcohol reduces the reaction rates, and longer reaction times are required hence, the reaction proceeds slowly (5 days) with tertiary alcohols (1-adamantanol) and requires higher catalyst loadings (20 mol%) to yield moderate yields (54%). 

Imidazolines are well known and certain derivatives, such as efaroxan 27, stimulate insulin secretion by binding to imidazoline I3 receptors <1999ANY(881)217>. Stability decreases as the number of heteroatoms increases 1,2,3-triazolines 28 are formed from azides as 1,3-dipolar cycloadducts but readily form the aromatic 1,2,3-triazole by oxidation or elimination. 

A simple, stereocontrolled, and economical synthesis of m-2,4,5-triarylimidazolines 276 starts from the reaction of aromatic aldehydes 274 with ammonia to form 2,4-diazapentadienes 275. Deprotonation of 2,4-diazapentadienes 275 with a strong base or under thermal conditions results in formation of the transient 2,4-diazapentadienyl anion that cyclizes in a disrotatory fashion to furnish m-imidazolines 276 (Scheme 134) microwave irradiation facilitates the ring closure <1997TL8631, 2003S1236, 2005H(65)353, CHEC-III(4.02.9.1.3)295>. 

However, the isolation of N,N -dimethyl substituted NHC [54] and the first saturated NHC, l,3-dimethyl-lH-imidazolin-2-ylidene by Arduengo et al. in 1995 [95] cast serious doubt as to the validity of the need for steric or aromatic stabilisation in these carbenes. Two independent theoretical studies by Boehme and Frenking [10] and Heinemann et al. [11] in 1996 as well as a later one by Tafipolski et al. [94] gave an excellent account of the stabilising factors and the differences between saturated and unsaturated NHC. 

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