An expedient one-step synthesis of polysubstituted guanidinoglucosides using HgO–4 Å molecular sieves as catalyst

The Application of 4Å Molecular Sieves in Organic Chemical Syntheses: An Overview

“…MS 4A has two roles in the reaction: it exchanges the lithium to sodium in the gallium complex, which increases the yield, and it can assist in the decomposition of the catalyst-product complex, thereby enhancing the overall reaction rate. In 2000, the group successfully achieved the catalytic asymmetric Michael addition of dimethyl malonate (55) to cyclohexenone (54) in the key step of the total synthesis of 19,20-dihydroakuammicine applying a heterobimetallic asymmetric catalyst, AlLibis(binaphthoxide) (ALB)-KOt-Bu-MS 4A (Scheme 16). 32 The authors found that the addition of 0.9 equivalent of the bases KO-t-Bu and MS 4A significantly improved the reaction.…”

“…The catalytic asymmetric Michael addition of dimethyl malonate (55) to cyclohexenone (54) Scettri and co-workers reported on the ability of MS 4A to dramatically enhance the catalytic properties of the applied Ti IV -calix [4]arene catalyst in the regio-and stereoselective epoxidation of allylic alcohols. 33 The formation of the desired products can be explained by a Sharpless type pathway that involves the coordination of both the allylic alcohol and t-butyl hydroperoxide at the metal centre, where MS 4A plays a critical role in increasing the ligand exchange rate of Ti IV chlorides and alkoxides.…”

“…Liu and Cao introduced the effective one-step synthesis of polysubstituted guanidinoglucosides 100 from peracetylated methyl 6-deoxy-6-thioureidoglucosides 98 using HgO-MS 4A as catalyst (Scheme 31). 55 In this reaction, HgO was applied as desulfurizing agent and MS 4A as dehydrating agent and alkaline catalyst for the one-step synthesis of a series of trisubstituted guanidino-containing sugars. When the reaction was carried out in the presence of MS 4A, a significant increase could be observed in the reaction rate, and the reaction was complete within 12 hours.…”

The chemistry and biology of organic guanidine derivatives

“…5 New methods of guanidine synthesis have been reported and are summarized in Table S1 †. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] With regards to yields and ease of preparation, the following methods are of particular interest: the synthesis of triflyl-substituted guanidines from aromatic isothiocyanates, in which the products can be further regiospecifically converted to unsymmetrically tetrasubstituted guanidines; 7 the synthesis of aromatic guanidines from symmetrical carbodiimides using dimethylaluminium chloride as catalyst; 8 a similar approach using samarium iodide; 9 aliphatic amines react with aromatic a-chloroaldoxime methanesulfonates in the presence of tetramethylethylenediamine (TMEDA) to give, after a reaction with either a primary or secondary amine, a tetrasubstituted guanidine via a Tiemann rearrangement; 12 the use of Yb(OTf) 3 as catalyst in the reaction of either primary aromatic or secondary aliphatic amines with carbodiimides give trisubstituted guanidines in good to excellent yields; 14 cycloguanidination of cyanodiaziridinimines on a terminal olefin, in order to obtain imidazolidin-2-imines regiospecifically at a terminal double bond; 15 synthesis of protected tetrahydro-1H-pyrrolo[1,2-c]imidazol-3(2H)-imines and hexahydroimidazo [1,5-a]pyridin-3(5H)imines from the corresponding 1-(2,2-disubstituted-but-3-en-1yl)guanidines and 1-(2,2-disubstituted-pent-4-en-1-yl)guanidines, in the presence of palladium acetate/copper chloride as catalyst; 18 a variety of aromatic and heteroaromatic amines can react with either symmetrical or asymmetrical carbodiimides to provide N,N 0 ,N 00 -trisubstituted guanidines in the presence of AlMe 3 in quantitative yield; 19 a very effective route for the preparation of (E)-benzyl 2-(tosylimino)imidazolidine-1carboxylates by a reaction between a benzyl 2-azidoethylcarbamate and tosylisocyanate, using bis(diphenylphosphino) butane as the azide-reducing agent; 22 guanylation of both primary and secondary amines can be performed with N-iodosuccinimide as the desulfurizating agent, in mo...…”