Sulfoxide complexes synthesis

Undoubtedly, one of the major interests in platinum-metal sulfoxide chemistry is the synthesis and use of O-bonded sulfoxide complexes as reactive intermediates in synthetic and catalytic chemistry. The chemistry of such weakly bonded intermediates has recently been reviewed (142). 

Synthesis and reactivity of Ru-, Os-, Rh-, and Ir-halide sulfoxide complexes with N-, P-, and S-heterocycles as ligands 04CRV4203. 

In this year, White et al. [113] reported highly effective synthesis of tricyclic lactone structure, which is a common structure of class I galbulimima alkaloids, through tandem allylic C-H activative alkylation/Diels-Alder reaction cascade of a-allylated y-butenolide 167 (Scheme 67). In the presence of Pd(II) bis(sulfoxide) complex, the reaction of 167 with active methane compoxmd 168 initially gave triene 169. Under the present conditions, 169 smoothly cyclized to give tricyclic lactone 170 as a mixture of endo/exo adducts in 75% yield. 

Mikolajczyk and coworkers have summarized other methods which lead to the desired sulfmate esters These are asymmetric oxidation of sulfenamides, kinetic resolution of racemic sulfmates in transesterification with chiral alcohols, kinetic resolution of racemic sulfinates upon treatment with chiral Grignard reagents, optical resolution via cyclodextrin complexes, and esterification of sulfinyl chlorides with chiral alcohols in the presence of optically active amines. None of these methods is very satisfactory since the esters produced are of low enantiomeric purity. However, the reaction of dialkyl sulfites (33) with t-butylmagnesium chloride in the presence of quinine gave the corresponding methyl, ethyl, n-propyl, isopropyl and n-butyl 2,2-dimethylpropane-l-yl sulfinates (34) of 43 to 73% enantiomeric purity in 50 to 84% yield. This made available sulfinate esters for the synthesis of t-butyl sulfoxides (35). 

Problems of dilution and pH sensitivity have also been encountered in the synthesis of cts-[Pt(S-R2SO)(olefin)Cl2] complexes (85), where deoxygenation of the sulfoxide with concomitant oxidation of the metal center occurs at low pH. The reactions of [M(Ph2PCH2CH2PPh2)Cl2] (M = Pd, Pt) with one equivalent of silver perchlorate in the presence of Me2SO yield either the O-Me O complex or its deoxygenation product, depending upon reaction conditions. A sequence of reactions, Eq. (27), has been proposed (143). 

The stereospecific conversion of sulfinates into sulfoxides of known chirality has been applied as a general method for determining the absolute configuration of a wide range of optically active sulfinic esters. For example, the absolute configurations of a series of alkyl alkanesulfinates obtained by asymmetric synthesis (107) or resolution via 3-cyclodextrin inclusion complexes (106) were determined by this method. 

The stem-loop structure in the noncoding 3 region of selenoprotein mRNAs has also been termed a SECTS element in mammals although it has a different overall structure. ° In silica analysis of the human genome sequence, using this consensus SECTS element along with the presence of the characteristic UGA codon within an exon, has led to the discovery of several new selenoproteins, including a selenium-dependent methionine sulfoxide reductase. It has been shown that a specific complex exists for selenoprotein synthesis that shuttles between the nucleus and the cytosol. This possibly protects the preformed complex for nonsense-mediated decay to allow for more efficient selenoprotein synthesis. The specific tRNA needed for selenocysteine... 

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