Sulfate esters cyclic

Diols can also be deoxygenated via Mv-sulfonate esters using sodium naphthalenide.294 Cyclic sulfate esters are also cleanly reduced by lithium naphthalenide.295... 

Carbolithium compounds of moderate reactivity open the O—C bond of cyclic sulfate esters or cyclic sulfamidates to produce new C—C links, as shown, for example, in equation 112 for a chiral cyclic sulfamidinate and 2-lithio-l,3-dithiane (380a). More reactive organolithium species, such as n-BuLi and PhLi, yield mixtures of products, probably due to attack on the S atom of the sulfonamido group too °. 

Acidolysis of cyclic sulfites with sulfuric acid and ester interchange with dimethyl sulfate produce cyclic sulfates (104). 

Whereas the phosphetanium (Sect. 2.2) derivatives undergo base-catalyzed hydrolysis with essentially complete retention of configuration, the reaction with the related thietanium salts proceeds with complete inversion of configuration and can be described simply as a direct nucleophilic substitution 35. As far as the author is aware, no exchange evidence of the type er countered in the acid-catalyzed hydrolysis of ethylene phosphate, has been found for the cyclic sulfate esters. Consequently despite the geometrical similarities between the cyclic sulfates and phosphates and the related hybridization of the central atoms, the situation in which a finite pentacovalent intermediate sulfur species exists has not been delineated (restricting the discussion to esters). 

Alternatively, the remaining sulfate ester of 70 may serve as a leaving group for a second nucleophilic displacement reaction. When this displacement is by an intramolecular nucleophile, a new ring is formed, as was first shown in the synthesis of a cyclopropane with malonate as the nucleophile [68] and of aziridines with amines as the nucleophiles [76]. The concept is further illustrated in the double displacement on (/J,/ )-stilbenediol cyclic sulfate (72) by benzamidine (73) to produce the chiral imidazoline 74 [79]. Conversion of the imidazoline (74) to (.V,.S )-stilbenediaminc 75 demonstrates an alternative route to optically active 1,2-diamines. Acylation of 75 with chloroacetyl chloride forms a bisamide, which, after reduction with diborane, is cyclized to the enantiomerically pure trans-2,3-diphenyl- 1,4-diazabicy-clo[2.2.2]octane (76) [81],... 

Tsuda M, Ishiyama H, Masuko K, Takao T, Shimonishi Y, Kobayashi J (1999) Keramamides M and N, Two New Cyclic Peptides with a Sulfate Ester from Theonella Sponge. Tetrahedron 55 12543... 

Reaction of cyclic sulfates with intramolecular O-nucleophiles leads to cyclic ethers and other heterocycles (Table 1). For example, a hydrolysis of compound 39 has produced predominantly the cyclic alcohols 41 (Scheme 4) < 1995JA12873 >. When the reaction was buffered with pyridine, the sulfate ester 40 was isolated rather than the free alcohol. An alcohol function in an intermediate product may give a route to a polysulfate cascade cyclization, which has been successfully realized in the synthesis of poly(tetrahydrofurans) (Table 1) <1995JA12873>. 

The resultant sulfate ester can be converted to the alcohol by acid hydrolysis. If an acid-sensitive group is present, this hydrolysis is still successful through use of a catalytic amount of sulfuric acid in the presence of 0.5-1.0 equivalents of water with tetrahydrofuran as solvent. The use of base in the formation of the cyclic sulfates themselves can also alleviate problems associated with acid-sensitive groups.174175... 

Cyclic sulfates can even be prepared from diols containing acid-sensitive groups acetonide, silyloxy) by reaction with thionyl chloride and N(C2H5)3 followed by oxidation of the isolated sulfites with Ru04 (catalytic). After reactions with a nucleophile, the resulting sulfate esters can be hydrolyzed by water (0.5-1.0 equiv.) in THF catalyzed by H2S04. The use of a minimal amount of water is crucial for chemoselectivity.2... 

In recent years, compounds of this type have received considerable interest as flavor components of various foodstuffs and as natural products of certain plant species (cf. Section 4.33.5.2). 1,3,2-Dioxathiolane derivatives, in the form of cyclic sulfite and sulfate esters, have been known since the turn of the century however, details of their structure and chemical behavior have only been studied during the last decades. 

Most compounds of this type are cyclic sulfite and sulfate esters of aromatic 1,2-diols as well as anhydrides of aromatic 1,2-disulfonic acids. The simplest representatives with unsubstituted benzene rings are 1,3,2-benzodioxathiole 2-oxide (48) (catechol sulfite), the corresponding 2,2-dioxide (156) (catechol sulfate) and 2,1,3-benzoxadithiole 1,1,3,3-tetroxide (158) (1,2-benzenedisulfonic anhydride). Compound (48) was synthesized by refluxing catechol with thionyl chloride in the presence of pyridine. In a similar fashion, from 2-mercaptophenol 1,2,3-benzoxadithiole 2-oxide was prepared (81AG603). The dioxide (156) was obtained in two steps by reaction of catechol monosodium salt with sulfuryl chloride in benzene at 0-10 °C and subsequent reflux of the intermediate (155) in the presence of pyridine. 

Dioxathiolane 2,2-dioxides (cyclic sulfate esters of 1,2-diols) are used in practice like sultones to introduce acid substituents into nitrogen heterocycles (48BSF1002), especially into cyanine dyes (58GEP1028718). Fluorinated derivatives are useful in the treatment of textiles such as cotton to impart wash and wear characteristics (62USP3055913). The conversion of cyclic sulfates into resinous film-forming polymers has been likewise patented (64USP3154526). 

The diols (97) from asymmetric dil droxylation are easily converted to cyclic sii e esters (98) and thence to cyclic sulfate esters (99).This two-step process, reaction of the diol (97) with thionyl chloride followed by ruthenium tetroxide catalyzed oxidation, can be done in one pot if desired and transforms the relatively unreactive diol into an epoxide mimic, ue. the 1,2-cyclic sulfate (99), which is an excellent electrophile. A survey of reactions shows that cyclic sulfates can be opened by hydride, azide, fluoride, thiocyanide, carboxylate and nitrate ions. Benzylmagnesium chloride and thie anion of dimethyl malonate can also be used to open the cyclic sulfates. Opening by a nucleophile leads to formation of an intermediate 3-sidfate aiuon (100) which is easily hydrolyzed to a -hydroxy compound (101). Conditions for cat ytic acid hydrolysis have been developed that allow for selective removal of the sulfate ester in the presence of other acid sensitive groups such as acetals, ketals and silyl ethers. 

Other Leaving Groups (Mitsunobu Reaction, Chlorosulfate Esters, Cyclic Sulfates)... 

Some polysaccharides carry negative charges, by virtue of their uronic acid components and/or modification of OH groups as sulfate esters or cyclic acetals of pyruvic acid (CH3COCOOH) these can often be precipitated by cationic surfactants such as cetyltrimethylammonium bromide. They can also be fractionated on weak anion exchangers. For neutral polysaccharides, elaborate precipitation protocols involving initial removal of proteins and nucleic acids have to be used - a useful precipitant of the polysaccharide is 50% ethanol. 

The telechelic PTHF, with terminal hydroxyl groups, is obtained by the hydrolysis of structure 7.7 with sulfate ester units (reaction 7.8). The products of hydrolysis are sulfuric acid and hydroxy-telechelic PTHF with a practically theoretical functionality (f), of 2 OH groups/mol, without unsaturation. It is very important that the content of cyclic oligomers is extremely low, practically negligible. 

The name cyclic sulfate originates from the sulfate ester of alcohols. Because in the present case the diol forms a part of the cyclic system, it is known as a cyclic sulfate. To avoid ambiguities, a systematic lUPAC nomenclature is required. Thus, the cyclic sulfite esters of 1,2-diols are named 1,3,2-dioxathiolane 2-oxides (1), and the corresponding cyclic sul-... 

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