Guanidine Compounds: Iv. Acetylation of Some Alkyl-Substituted Guanidines With Acetic Anhydride and Ethyl Acetate

Abstract

'fhc acctylatiorl of some mono-, N,N-, and N,Nf-diallcylguanidi~les was studied using c~h y l acetate and acetic anhydride. Except for the N,N-diallcylguanidines, the action of ethyl acetate on the free bases gave monoacetyl derivatives. Acetic anhydride with the acetate salts gave diacetyl derivatives with monoalliylguanidines, acetamido-1,3,5-triazines with N,N-dialkylguanidi~les, and unstable di-and tri-acetyl derivatives with N,N'-diallcylguanidines. The assignment of symmetrical structures to the mono-and tri-acetyl derivatives and an asymmetrical structure to the diacetyl Gerivatives was supported by nuclear magnetic resonance spectra. The ultraviolet spectra of the monoacetyl derivatives exhibited one peal; in the region 230-235 mp whilst the diacetyl derivatives showed two pealcs in the regions 220-230 mp ancl 253-263 mp. Some comments are made on the infrared spectra of these compounds.In an earlier paper in this series Cockburn and Bannard (1) reported the for~nation of amino-(I) and acetarnido-s-triazines (11) on acetylation of alkylguanidine saIts under vigorous conditions. R'R" I. R = H ; R', R" = H or all;yl 11. R = CH3CO; R', R" = H or allcyl 111. R = CH3CO; R', R" = CH, Iiyabinin (2) had previously show11 that the products obtained on acetylation of guanidine acetate were dependent on the conditions used. Under mild conditions, an acetylated guanidine derivative was obtained rather than an s-triazine derivative. The present study, in which the acetylation of several mono-, N,N-, and N,N1-diallcylguanidines with ethyl acetate and acetic anhydride was esamined, revealed that the type of allcyl substitution also influenced the product obtained. T h e opportunity was talcen t o examine the infrared and ultraviolet spectra of the acetylated guanidines isolated.Various conditions for the acetylation of trans-2-guanidocyclohexanol with acetic anhydride were examined t o determine which gave the highest yield of acetylated products. T h e addition of sodiunl acetate did not influence the yields and was therefore omitted, since it merely complicated isolation of the products. I t was found that a shorter time of heating a t 100' than that previously employed for the acetylation of guanidine (3) was beneficial, since even the relatively stable diacetyl derivatives were degraded or cyclized on prolonged heating with acetic anhydride a t this temperature.

Nuclear Magnetic Resonance and Infrared Studies of Acylated Imidazolidinones and Imidazolidinethiones

“…spectroscopy for assigning structures and conformations in acylated 2-0x0-, 2-thio-, and 2-imino-imidazolidines have not in the past been fully exploited. We have used it to differentiate between the several structures suggested for triacetyl-2-imino-imidazolidine on the basis of its infrared spectrum (1). More recently Roberts (2) has also used n.nl.r.…”

Acyl guanidine functional poly(2‐oxazoline)s as reactive intermediates and stimuli‐responsive materials

“…In addition, when the UV–vis absorbance of the polymer was compared to the starting material in acidic media, an additional absorbance at ±235 nm was observed (Fig. S9), which is in accordance with the characteristic absorbance of acyl guandines . Since we could not confirm the effect of the guanidinylation reaction on the molecular weight distribution due to the insolubility of the polymer, we opted to repeat the reaction on the synthesized copolymers, in order to mitigate the insolubility in organic solvents.…”

“…This precipitate turned out to be the desired polymer, which could be isolated after washing the sodium chloride away with methanol. This protocol was inspired on literature for the preparation of small molecule acyl guanidines . Due to its high polarity, the obtained polymer was insoluble in most organic solvents, including ACN, methanol and N,N‐ dimethylacetamide, which impaired the analysis via the available SEC equipment.…”

“…Inspired by the guanidine‐catalyzed amidation and transesterification of polymers with pendant ester groups, we explored the use of guanidines as a reactant, rather than a catalyst, in order to synthesize the corresponding acyl guanidines. While the acyl guanidine adduct is a reactive intermediate that is formed during guanidine‐catalyzed acylations (Scheme ), we hypothesized that this intermediate could be isolated, as multiple literature reports have shown the formation and isolation of stable guanidine adducts in guanidine‐catalyzed reactions . Also recently, the synthesis of a triazine heterocycle was successfully performed via an acylated metformine intermediate starting from ester‐functional PAOx .…”

Some Aspects of Guanidine Secondary Metabolites

“…In the ultraviolet absorption region (33)(34)(35)(36) simple non-conjugated guanidine compounds exhibit a weak absorption at Amax 265 nm (I: = 15, H 2 0) and a stronger absorption below Amax 220 nm (5600 < I: < 39).…”