Isocyanates amidines

As representative examples for the reactivity of the Cp Ti(amidinate) complexes some reactions with CS2 and COS are shown in Scheme 88. Other reagents that have been investigated in this study include carbodiimides, isocyanates, CO2, PhNO as well as aldehydes, ketones, and imines. ... 

Reactions of the cyclopentadienyl-amidinate-supported imidotitanium complexes with CO2 proceed via initial cycloaddition reactions, but depending on the imido Af-substituent go on to yield products of either isocyanate extrusion or unprecedented double CO2 insertion (Scheme 89). ... 

Structurally related complexes are also active initiators for the living polymerization of carbo-diimides (which are isoelectronic to isocyanates).1003 The proposed intermediate for this polymerization process is a metal amidinate (Scheme 29), and the model complex (349) has been reported to be a highly efficient catalyst, polymerizing 500 equivalents of di- -hexylcarbodiimide in less than 10 s. A more hydrolytically robust series of initiators has also been developed, based upon copper(I) and copper(II) amidinates.1004... 

Coreactants, in microencapsulation, 16 444 Coreactive curing agents, 10 388-389, 392-411, 418. See also Curing agents amine functional, 10 392 401 carboxylic functional polyester and anhydride, 10 401—406 cyanate ester, 10 411 cyclic amidine, 10 410 isocyanate, 10 410 melamine-, urea-, and phenol-formaldehyde resins,... 

When the side chain involves an unsymmetrical urea moiety, muscle relaxant activity is often seen. One such agent, 1id-amidine (2) exerts its activity as an antiperistaltic agent. Its synthesis involves the straightforward reaction of 2,6-dimethyl phenyl isocyanate and ji-methylguanidine. ... 

Amidines formed by condensation of 4-aminouracils with dimethylformamide dimethyl acetal are effective dienophiles, and form pyrimido[4,5-rflpyrimidines by [4-I-2] cycloaddition with isocyanates, isothiocyanates (Equation 83) <2005TL1433> and imines (Equation 84), A similar process has also been reported, using a nitrone as the dienophile (Equation 85) <2006BMCL3537>. 

Perfluoroalkyl isocyanates react with stoichiometric quantities of primary amines at low temperatures to yield perfluoroalkylureas, and with secondary amines to yield perfluoroacyl amidines [91] (Eq. 60). 

Addition of aryl isocyanates to N-substituted amidines at elevated temperatures [89]. 

Synthesis from amidines, isocyanates, aldehydes and ketones 512... 

The reaction between amidines and N-chlorocarbonyl isocyanate gives the ionic compounds (133 Scheme 71). If the amidine is replaced by a urea, the 1,3-disubstituted isocyanurate (134) is formed in very good yield. Even potentially labile substituents, e.g. f-butyl, survive this reaction intact. Thioureas also may be used they form salts (135) which... 

The isocyanates play a most important role in the syntheses of l,3,5-triazine-2,4-diones. Two equivalents of the isocyanate react with an equivalent of another reagent, usually an amidine or imine, to yield the desired products. Once again the reaction occurs via a dipolar intermediate (165 Scheme 103) (see Sections 2.20.4.5.3 and 2.20.4.6.1). 

The kinetics and mechanism of the phosphorus-catalysed dimerization of acrylonitrile to give 1,4-dicyanobut-l-ene and 2,4-dicyanobut-l-ene have been studied.114 The reactions of aryhminodimagnesium (138) with //-substituted p-cyanobenzophenones, l-cyano-9-fluorenenone, o-, m-, and p-dicyanobcnzcnes, and o-, m-, and p-nitrobenzonitriles have been examined.115 The effect of pressure on the reaction of 3 -methyl- l-(4-tolyl)triazene (139) and benzoic acid in chloroform and acetonitrile has been studied.116 The effect of acids on the rate of urethane formation from alcohols and isocyanates in the presence of alkyltin carboxylates has been examined.117 A Hammett a value has been reported for the amidine group N=CHNMe2 and used for the prediction of the basicity of sites in bifunctional amidines.118... 

A general procedure for the synthesis of 5-chloro-l,2,4-thiadiazoles (289) is the reaction of amidines with trichloromethylsulfenyl chloride (329) in the presence of an acid acceptor (Scheme 152) (also see Scheme 102). 3-Halo derivatives (387 X = Cl, Br, I Scheme 153) have been obtained in moderate yields from the corresponding amines (386) using the Sandmeyer-Gatterman reaction (Scheme 153) (60JCS3234) (see Section 4.25.3.3.4). 3-ChIoro-l,2,4-thiadiazolin-2-ones of types (298) and (299) can be prepared by treatment of chlorosulfenylcarbonyl chloride (291) with carbodiimides and cyanamides, respectively (Scheme 154) (70AG(E)54). The isomeric products (270) and (274) are produced by the chlorination of mixtures of isocyanates and isothiocyanates (Scheme 155) (see also Scheme 95). 

Weakly electrophilic aliphatic isocyanates and carbodiimides are good reaction partners toward 44. The overall reaction is an acylation which leds to an easy shortcut to push-pull secondary amides 57 and amidines 58. A few examples follow (97) 138), (98)147 , 48>... 

Expectedly, chloroformiate introduces an ester group 34,38) whereas isocyanates, isothiocyanates and carbodiimides lead to the respective push-pull aminodiyne amides, thioamides and amidines (132-135) 34,37). 

The use of dicarbodiimides as monomers in polyaddition reactions have not as yet found wide utility. However, polymers containing carbodiimide groups are known, and further nucleophilic reactions of these polymers with numerous substrates are reported. Carbodiimides, generated in situ from isocyanates are used as catalyst in the formation of polyamides from diisocyanates and dicarboxylic acids. Also, homoleptic lanthanide amidinates, made from carbodiimides, exhibit high catalytic activity for the ring opening polymerization of e-caprolactone at room temperature. ... 

Ge amidinate complexes are susceptible to oxidation of elemental chalcogens. Many of these complexes are excellent catalysts for the cycUzation of aryl isocyanates. ... 

Imidazoles can also be made by heating 4-tosyloxazolines in saturated methanolic ammonia or monoalkylamines. These reactions proceed through intermolecular condensation of a-aminoketones and amidines and intramolecular cyclization of a-ainidinoketones, respectively [49] (see Section 4.2). When A -unsubstituted 4-oxazolin-2-ones are added to isocyanates, the 2-oxo-4-oxazoline-3-carboxamide products cleave under the influence of strong acids and heat. Subsequent ring closure gives 4-imidazolin-... 

It is well known that halomethyleneiminium salts, often prepared in situ (see Section 2.1.2.2) react with ammonium salts, primary amines, secondary amides, urea and IV-substituted ureas to afrbrd amidinium salts, from which the free amidines can be obtained by addition of bases. > 4 Some recent results are given below. Dimethylformamide chloride and other 7V,iV-disubstituted formamide chlorides were reacted with acetanilides, chloroacetanilides, 6-aminopenam derivatives, 2-aminopyrimidine, 4-aminouracil, 2-amino-4-chloropyridazine, 2-aminothiazole, 2-aminobenzothiazole and thiobenzamides to give the amidines via the amidinium salts. In the reaction of MA -disubstituted formamide chlorides with thiobenzamides the solvent seems to be decisive for the course of the reaction. In tertiary formamides the thiobenzamides are desulfurized to nitriles, whereas in CHCI3 or CCI4 amidinium salts (296 Scheme 45) are formed. From trimethylsilyl isocyanate and the fluorinated amine (297) the /V-fluorocarbonylamidine (298) is accessible. ... 

Complexes of organotin with amidines have been found to be excellent catalysts for the preparation of polyurethane foams, which do not have the disadvantage of any amine odor and, in addition, delayed onset of the isocyanate-hydroxyl reaction An example of a mercapto-delayed organotin catalyst is 2,2,4,4-tetrakis(alkyl)- l,3,2,4-dithia-stannetane.55 Amine salts of amino acids, tertiary amino acids, and tertiary amino acid-nitrile compositions, have been found to be effective as delayed action catalysts for polyurethane synthesis. They are particularly effective when used in combination with an organometallic compound, such as an organotin. ... 

The iV-acyl ureas 157, prepared by amidine rearrangement (Section II.B.3), undergo thermal elimination of phenyl isocyanate with formation of the amides 158 (Eq. (24)) (01JCS(P1)680). This approach provides access to amides of unstable 2-aminofurans that cannot be prepared by acylation of the primary amine. 

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