Dithioacetals complexes

PdLj, [PdLj]2 Dithioacetate complex. Three distinct modifications 14... 

Dithioacetate complex. Three distinct modifications 14 known, all 2 1L Pd ratio. One contains alternate mononuclear and binuclear (bridging L) units stacked in columns (X-ray structure), one contains dimers only (X-ray structure), while the structure of the third form is not established From insertion of CS2 into fraru-[PdMeI(PMe3)2] IS... 

Various bidentate ligands like dithiocarbamate afford monomeric square planar complexes specific examples are Pt(S2CNEt2)2 and Pt(Se2CNBu)2 (confirmed by X-ray). A similar structure is found for the dithiobenzoate Pd(S2CPh)2 one form of the dithioacetate is dimeric, a second form is a mixture of monomers and dimers. 

The dithioacetate is a tetramer, still with digonally coordinated gold [100]. Though long known, the gold complexes of terpenethiolates ( liquid gold )... 

The reaction of methylenesulphones with allyl halides in the presence of quaternary ammonium salts produces the 1-allyl derivatives [52], unlike the corresponding reaction in the absence of the catalyst in which the SN- product is formed (Scheme 6.5). In contrast, alkylation of resonance stabilized anions derived from allyl sulphones produces complex mixtures [51] (Scheme 6.6). Encumbered allyl sulphones (e.g. 2-methylprop-2-enyl sulphones) tend to give the normal monoalkyl-ated products. Methylene groups, which are activated by two benzenesulphonyl substituents, are readily monoalkylated hydride reduction leads to the dithioacetal and subsequent hydrolysis affords the aldehyde [61]. 

It should be mentioned here that nucleophilic titanium carbene complexes, generated in situ from dithioacetals and Cp2Ti[P(OEt)3]2 (see e.g. Sections 3.2.2.1 and 3.2.4.2), can undergo M-H insertions with silanes, germanes and stannanes [694]. This reaction represents an interesting alternative procedure for the che-... 

A series of reagents have been developed which are prepared in situ from a geminal dihalide or a dithioacetal [635,730] and a transition metal complex. Titanium-based reagents of this type olefinate a broad range of carbonyl compounds, including carboxylic acid derivatives (Table 3.12), and are a practical alternative to the use of isolated carbene complexes. 

Apart from the tandem metathesis/carbonyl o[efination reaction mediated by the Tebbe reagent (Section 3.2.4.2), few examples of the use of stoichiometric amounts of Schrock-type carbene complexes have been reported. A stoichiometric variant of cross metathesis has been described by Takeda in 1998 [634]. Titanium carbene complexes, generated in situ from dithioacetals, Cp2TiCl2, magnesium, and triethylphosphite (see Experimental Procedures 3.2.2 and 3.2.6), were found to undergo stoichiometric cross-metathesis reactions with allylsilanes [634]. The scope of this reaction remains to be explored. 

The stoichiometric equivalents of halofluorides have been recently applied to transform alkylene dithioacetals into gcm-difluorides.70-71 Dithioacetals such as 1,3-dithiolanes and 1,3-dithianes arc readily obtained from the corresponding carbonyl compounds by the reaction with ethane-1,2-dithiol or propane-1,3-dithiol in the presence of the complexes boron trifluoride-bis(acetic acid) or boron trifluoride-diethyl ether. Using a two-step procedure, a range of aldehydes and ketones can be converted into gem-difluorides under mild conditions. 

A related complex is the dithioacetate [(AuS2CMe)4] prepared from NafAuCLt] and MeCS2H. This forms a tetrameric unit (22) in which all four Au—Au bond distances are 301 pm.282... 

Dithioacetic acid, phenyl-metal complexes, 646 Dithiobenzoic acid metal complexes, 646 colours, 646 Dithiobiuret metal complexes, 640 Dithiocarbamic acid metal complexes, 585 Ditbiocarbazic add metal complexes, 803 Dithiocarbimic acid metal complexes, 588 Dithiocarbimic acid, cyano-metal complexes, 808 Dithiocarboxylic acids... 

Coupling of dithioacetals with RMgX butadienylsilanes.1 This coupling is possible when catalyzed by Ni(H). Thus 2-(2-phenylethenyl)-l, 3-dithiolane (1) couples with (trimethylsilyl)methylmagnesium chloride in THF in the presence of this nickel complex to form (E,E)-trimethyl(4-phenyl-l,3-butadienyl)silane (3) in 91% yield. 

Selective Organic Electrofluorination. The electrogeneration of fluorine from the electrolysis of a mixture of KF and HF has been well known for many decades. Organic perfluorination using HF and HF/KF is used widely. Now the use of HF complexes with tetraalkylammonium fluoride has led to the anodic difluorination of dithioacetals. 

All types of electrophiles have been used with 2-lithio-l,3-dithiane derivatives, including alkyl halides, sulfonates, sulfates, allylic alcohols, arene-metal complexes, epoxides, aziridines, carbonyl compounds, imines, Michael-acceptors, carbon dioxide, acyl chlorides, esters and lactones, amides, nitriles, isocyanates, disulfides and chlorotrialkylsilanes or stannanes. The final deprotection of the dithioacetal moiety can be carried out by means of different types of reagents in order to regenerate the carbonyl group by heavy metal coordination, alkylation and oxidation184 or it can be reduced to a methylene group with Raney-nickel, sodium or LiAIII4. 

Interestingly, the subsequent reactions of the titanium-alkylidene species 12 obtained from dithioacetals are not limited to carbonyl olefina-tions. When the carbene complex is prepared in the presence of olefins, the latter are smoothly cyclopropanated (Scheme 8 13) [14]. Furthermore, the reaction of symmetrically disubstituted acetylenes with dithioacetals containing a methylene unit provides the corresponding trisubsti-tuted 1,3-dienes 14 in a stereoselective fashion 115]. 

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