Guanidine aromatic

Dimethyl carbonate, (Bu2N)2C=NMe, 180°, 4.5 h, 54-99% yield. In the presence of this guanidine, aromatic methyl carbonates are converted to methyl ethers with loss of CO2. 

Dimethyl carbonate, (Bu2N)2C=NMe, 180°C, 4.5 h, 54-99% yield. In the presence of this guanidine, aromatic methyl carbonates are converted to methyl ethers with loss of CO2. The reaction can also be carried out with K2CO3 at 140°C in triglyme or DMF, 60-81% yield or with CS2CO3 at 120°C in neat dimethyl carbonate." In the latter case, simple alcohols are converted to methyl carbonates. DBU can be used as a base in this process, either at 90°C or with... 

There is an abundance of substances with denaturing action namely, acids, bases, organic solvents, concentrated solutions of urea or guanidine, aromatic acids, like salicylic acid, and detergents, such as dodecylsulfate. Proteins are not all equally susceptible to these substances nor... 

Didemnum Phenylethylamlne derivatives pyridoacridines alkaloids of pyrrole (lamellarins), Indole (eudistomins), carbazole and guanidine aromatic and heteroaromatic S/N derivatives (thiazole-rich cyclic peptides) halogenated nucleosides... 

Guanidines. Guanidines (10) were one of the first aniline derivatives used as accelerators. They are formed by reaction of two moles of an aromatic amine with one mole of cyanogen chloride. Diphenylguanidine (DPG) has enjoyed a resurgence ia demand as an activator for sulfenamides and a co-accelerator ia tire tread compounds which employ siUca fillers for low rolling resistance. Guanidines alone show too Htde activity to be extensively used as primary accelerators. There were no U.S. producers as of mid-1996. 

The guanidine function, when attached to an appropriate lipophilic function, often yields compounds that exhibit antihypertensive activity by means of their peripheral sympathetic blocking effects. Attachment of an aromatic ring via a phenolic ether seems to fulfill these structural requirements. Alkylation of 2,6-dichlorophenol with bromochloroethane leads to the intermediate, 58. Alkylation of hydrazine with that halide gives 59. Reaction of the hydrazine with S-methylthiourea affords the guanidine, guanoclor (60). ... 

The formation of a bis(guanidinate)-supported titanium imido complex has been achieved in different ways, two of which are illustrated in Scheme 90. The product is an effective catalyst for the hydroamination of alkynes (cf. Section V.B). It also undergoes clean exchange reactions with other aromatic amines to afford new imide complexes such as [Me2NC(NPr )2]2Ti = NC6F5. ... 

FD-MS is also an effective analytical method for direct analysis of many rubber and plastic additives. Lattimer and Welch [113,114] showed that FD-MS gives excellent molecular ion spectra for a variety of polymer additives, including rubber accelerators (dithiocar-bamates, guanidines, benzothiazyl, and thiuram derivatives), antioxidants (hindered phenols, aromatic amines), p-phcnylenediamine-based antiozonants, processing oils and phthalate plasticisers. Alkylphenol ethoxylate surfactants have been characterised by FD-MS [115]. Jack-son et al. [116] analysed some plastic additives (hindered phenol AOs and benzotriazole UVA) by FD-MS. Reaction products of a p-phenylenediaminc antiozonant and d.v-9-lricoscnc (a model olefin) were assessed by FD-MS [117],... 

Completion of the total synthesis afforded only six further steps, including the installation of the second 2-aminopyrimidine ring via a second domino sequence. This process presumably involves a conjugate addition of guanidine (2-293) to the enone system of2-292, followed by a cyclizing condensation and subsequent aromatization. Under the basic conditions, the ethyl ester moiety is also cleaved and 2-294 is isolated in form of the free acid, in 89 % yield. Finally, decarboxylation and deprotection of the amino functionality yielded the desired natural product 2-295. 

Similarly, Hafez and co-workers <00JCR(S)13>, as well as Al-Afaleq <00SC1985>, prepared 2-aminopyrimidines 26 from the conjugate addition of guanidine 25 to enaminones 24 followed by ring closure and aromatization. 

GABA HMG-CoA HMPA HT LDA LHMDS LTMP NADH NBH NBS NCS NIS NK NMP PMB PPA RaNi Red-Al RNA SEM SnAt TBAF TBDMS TBS Tf TFA TFP THF TIPS TMEDA TMG TMP TMS Tol-BINAP TTF y-aminobutyric acid hydroxymethylglutaryl coenzyme A hexamethylphosphoric triamide hydroxytryptamine (serotonin) lithium diisopropylamide lithium hexamethyldisilazane lithium 2,2,6,6-tetramethylpiperidine reduced nicotinamide adenine dinucleotide l,3-dibromo-5,5-dimethylhydantoin A-bromosuccinimide A-chlorosuccinimide A-iodosuccinimide neurokinin 1 -methyl-2-pyrrolidinone para-methoxybenzyl polyphosphoric acid Raney Nickel sodium bis(2-methoxyethoxy)aluminum hydride ribonucleic acid 2-(trimethylsilyl)ethoxymethyl nucleophilic substitution on an aromatic ring tetrabutylammonium fluoride tert-butyldimcthyisilyl fert-butyldimethylsilyl trifluoromethanesulfonyl (triflyl) trifluoroacetic acid tri-o-furylphosphine tetrahydrofuran triisopropylsilyl A, N,N ,N -tetramethy lethylenediamine tetramethyl guanidine tetramethylpiperidine trimethylsilyl 2,2 -bis(di-p-tolylphosphino)-l,r-binaphthyl tetrathiafulvalene... 

A double tethered Biginelli reaction was carried out on the simple five-membered urea aldehyde 305 that reacted with the aliphatic and aromatic bis-ketoesters 306 and 307 giving compounds 308 and 309, respectively, in good yield, albeit with a diasteromeric ratio of 1 3. A series of different polycyclic bis-guanidines resembling betzelladine alkaloids were prepared <2003OL4485>. 

C. R. Coan, L. M. Hinman, and D. A. Deranleau, Charge-transfer studies of the availability of aromatic side chains of proteins in guanidine hydrochloride, Biochemistry 14, 4421 4427... 

Certain aromatic guanidines (and biguanides) are known to cause a reflex fall of blood pressure and heart rate by an action on receptors in the heart [288]. However, there have been no reports of arylguanidines exhibiting activity at sympathetic nerve endings. o-Bromophenylguanidine (LXXIV) does not affect cat nictitating membranes [239]. 

The chiral guanidine s role as a strong Brpnsted base for the reactions of protic substrates has been proposed. In 1999, Corey developed a C -symmetric chiral guanidine catalyst to promote the asymmetric Strecker reaction [117]. The addition of HCN to imines was promoted high yields and high enantioselectivities for both electron-withdrawing and electron-donating aromatic imines (Scheme 64). 

Dealing with the synthesis of dihydropyridopyrimidinones, the procedure was quite similar to the precedent, involving 2,6-diaminopyrimidin-4(3//)-one as enaminocarbonyl partner, various 1,3-dicarbonyl derivatives, and either aliphatic or aromatic aldehydes in water under microwave irradiations (Scheme 11). Interestingly, the guanidine system was unreactive, and a library of tri- and tetracyclic dihydropyridopyrimidinone derivatives was chemoselectively synthesized in high yields and short reaction times from this environmentally friendly procedure. 

Ooi has recently reported application of chiral P-spiro tetraaminophosphonium salt 37 as a catalyst for the highly enantio- and diasterioselective direct Henry reaction of a variety of aliphatic and aromatic aldehydes with nitroalkanes (Scheme 5.51) [92]. Addihon of the strong base KO Bu generates in situ the corresponding catalyhcally active triaminoiminophosphorane base A. Ensuing formation of a doubly hydrogen-bonded ion pair B positions the nitronate for stereoselective addition to the aldehyde. This catalyst system bears many similarities to guanidine base catalysis. 

However in the dpg/dpg+ systems, the influenee of hydrogen bonds between the guanidine group and other moleeules is not the sole faetor influencing aromaticity, since the interaction between the guanidinium delocalized t -orbitals and the ring ti-orbitals is also very important. 

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