Sulfonyl with guanidines

It may be prepared by eondensing /7-amino benzene sulfonyl ehloride with guanidine and hydrolysing the resultant in the presenee of sodium hydroxide. 

This sequence is equally applicable to keto esters. Thus, condensation of guanidine with ethyl acetoacetate gives the pyrimidone, 134. Elaboration as above gives the pyrimidine, IJ5 acylation with the sulfonyl chloride (88) followed by hydrolysis yields sulfamerazine (107). Reaction of guanidine with beta dicarbonyl compounds gives the pyrimidine directly. Condensation of the base with acetonyl acetone affords the starting amine for sulfadimidine (108). ... 

The guanidine moiety was incorporated by dimethyl (2,2,5,7,8-pentamethylchromane-6-sulfonyl N-alkylated amino) dithiocarbonate[264] (Pmc-dithiocarbonate) 91 in two steps. One methylsulfanyl group was replaced by the primary amino group of Bzl-Norn-OBzl in the presence of excess DIPEA and the isothiourea obtained was reacted with silver nitrate under basic conditions to yield the intermediate sulfonylcarbodiimide which reacts immediately with ammonia to yield the guanidine Bzl-Narg(Pmc)-OBzl 91. 

Sulfonyl resins (23) have been developed to prepare indoles via a palladium-catalyzed cyclization. Cleavage was carried out with TBAF with excellent yields and purities (85-100%) [78]. Likewise, a library of bivalent ligands (including guanidine, pyridinium and carboxylic and sulfonic acids constituents) for a protein receptor was prepared on nitrobenzenesulfonamide resin 24. Cleavage was achieved with sodium sulfide [79]. 

In the first step, amines react with 3-(methylsulfanyl)-l,4,2-benzodithiazines to give the corresponding 3-amino compounds (see Section 1.4.6.1.3.1), which may be ring opened by further treatment with a second molecule of amine to afford 2-[(2-sulfanylphenyl)sulfonyl]guanidines... 

Starting from an intermediate l,4,2-benzodithiazin-3-amine, reaction with a different amine yields unsymmctrically substituted 2-[(2-sulfanylphenyl)sulfonyl]guanidines 3.53... 

In fact, under homogenous reaction conditions it was found that the SET mechanism prevailed, affording phenylsulfonyl-derivative 108 as the major product. Similar reactivity patterns were observed in guanidine analogues, with sulfonylation of the 2-NH2 group occurring as the most common side product. 

In 2009, Feng and coworkers developed new guanidine catalysts with an amino amide skeleton [139]. Among the various catalysts tested, guanidine 49 was found to be the most active for the enantioselective Michael reaction of a (i-ketoester with nitroolefins (Scheme 10.46). The conjugate addition products were obtained in high yields and excellent diastereo- and enantioselectivities. The same researchers used bis-guanidine catalysts for the enantioselective inverse-electron-demand hetero-Diels-Alder reaction of chalcones with azlactones (Scheme 10.47) [140] and enantioselective Mannich-type reaction of a-isothiocyanato imide and sulfonyl imines (Scheme 10.48) [141]. 

In 2007, Ooi and coworkers introduced chiral tetraaminophosphonium salts as a new class of Bronsted acids [166]. Similar to the guanidine/guanidinium case, these tetraaminophosphonium salts act as Bronsted bases in their neutral/ deprotonated (triaminoiminophosphorane) form, while they can also be used as mono-functional Bronsted acids in their protonated, phosphonium form. Phos-phonium salt 67, when neutralized in situ with KO Bu, was shown to be a highly effective catalyst in the enantioselective Henry reaction of nitroalkanes with various aromatic and aliphatic aldehydes (Scheme 10.65). The same strategy was further applied to the catalytic asymmetric Henry reaction of ynals [167] and hydrophosphonylation of ynones (Scheme 10.66) [168]. Brfunctional catalysis using this scaffold were also obtained using the carboxylate salts of tetraaminophosphoniums in the direct Mannich reaction of sulfonyl imines with azlactones (Scheme 10.67) [169]. 

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