CESIUM THIOLATES

Ceric ammonium nitrate Cerate(2-), hexanitrato-, diammonium Cerate(2-), hexakis(nitrato-O)-, diammonium, (OC-6-11) (16774-21-3), 67,141 Cerium(ill) chloride, heptahydrate (18618-55-8), 69, 89 Cesium carbonate Carbonic acid, dicesium salt (534-17-8), 65, 150 CESIUM THIOLATES, 65, 150 Chiral auxiliary, 65, 173, 183, 203, 215 Chiral oxazolidinone auxiliary, from phenylalanine, 68, 77, 83 Chirasil-Val, 66, 153, 154... 

SYNTHESIS OF MACROCYCLIC SULFIDES USING CESIUM THIOLATES 1,4,8,11-TETRATHIACYCLOTETRADECANE... 

The yields of macrocyclic dithiacycloalkanes 61 in cyclization reactions were significantly increased by the introduction of cesium thiolates by Buter and Kellogg [17, 58]. TTie synthesis of the cyclic sulfides was performed by the reaction of dibromc lkanes with the cesium thiolates 60 under dilution conditions [1] in DMF as solvent. 

Vogtle and Meurer explained the favoured formation of strain ring compounds in the synthesis of cyclophanes by cyclizations with cesium thiolates by a preorientation (preorganization) of the reactants at the cesium cation [82], For the cesium ion in contrast to the smaller alkali metal cations the capabiUty of forming an 11-membered intermediate is ascribed, which would favour an intramolecular course of the reaction (Fig. 4). 

Synthesis of Macrocyclic Sulfides Using Cesium Thiolates... 

The related pentakis-TTF derivatives 41, synthesized by Becher et al. by reaction of tetraiodide 39 with four equivalents of the thiolate anion liberated upon treatment of 40 with cesium hydroxide (Scheme 9), displayed qualitatively similar redox behavior to 38 with noninteracting TTF units. The attachment of branched multiredox wedges (e.g. 32) to the tetrathio-TTF core should provide interesting systems in which a central TTF unit may be shielded by the outer layers and should oxidize more readily. 

The amino group can be protected by forming its sulfonyl [such as arylsulfonyl or 2-(trimethylsilyl) ethyl sulfonyl], sulfenyl and silyl derivatives. The 2- or 4-nitrophenylsul-fonamide derivatives of amino acids are useful substrates for mono-N-alkylation using only cesium carbonate (CS2CO3) as the base. The sulfonamide group can be removed in 1.89 by potassium phenyl thiolate (PhSH and K2CO3) in acetonitrile to give the N-alkylated a-amino esters 1.90 and the reaction occurs without racemization. 

Reaction of the monocyanoethyl-protected TTF 738 with cesium hydroxide in a mixture of methanol and DMF led to the deprotected thiolate, which was further alkylated with the bromobutyl-substituted MOM-triptycene 739 to give the MOM-TTF 740 in 89% yield (MOM = methoxymethyl). The MOM protecting group was removed quantitatively under acidic conditions and the resulting hydroquinone was oxidized to yield the TTF-quinone 741 in 54% yield (Scheme 109). The preparation of the pyrrolo-TTF derivatives 25 was accomplished in a similar way <1998JOC1198>. 

Structurally rather complicated target molecules can be synthesized with the aid of thiolate 1,6-addition reactions to acceptor-substituted dienes as weU. For example, a richly functionalized proline derivative with a 2,4-pentadienal side chain was converted into the corresponding 6-phenylthio-3-hexen-2-one derivative by 1,6-addition of phcnylthiolate, treatment of the adduct with methyl lithium and oxidation (equation 46) . The product was transfonned into acromelic acid A, the toxic principle of clitocyhe acromelalga ichimura. Similarly, the 1,6-addition reaction of cesium triphenylmethylthiolate to methyl 2,4-pentadieuoate served for the construction of the disulfide bridge of the macrobicyclic antitumor depsipeptide FR-901,228 - . 

A synthesis of the 4-thiogalabioside (90) has been reported whereby the thiolate of 91, generated by treatment with cesium carbonate, has been condensed with the, 2-cis chloride 92 in good yield (85%) [48] (Scheme 18). 

The shackled victim, an a,w-bis(3-tosyloxypropyl)oligosilane, was attached to the rack by treatment with cesium [m]staflane-1 3(m-i)dithiolate to form the macrocycles 1[2,6] or 1[2,8] bydito-sylalkyl/Cs-thiolate macrocyclization (50). 

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