Dithioketene acetals

Dithioketene acetals have been synthesized by stirring of substrates 264 with butane-1,4-dithiol at 30-35 °C (Scheme 81) <2002PS2529>. 

Second Encounter with Sulfur—Interaction of an Enamine and a Dithioketene Acetal... 

A catalytic version of this reaction has also been developed by Mukaiyama and co-workers (Scheme 35) (72). Addition of the trimethylsilyl dithioketene acetal 35.1 to the enone in the presence of the amine-tin(II) triflate complex gives nearly identical yields and optical purities as the stoichiometric procedure. 

Dithiocarboxylic acid derivatives also provide a useful route to dithioketene acetals (another name for ketene dithioacetals).Treatment of dithiopropionic acid (376) with excess LDA (for 0-alkylation reactions... 

The synthesis of a perfluoroalkyl dithioketene acetal is shown in Scheme 10. If 0-3 in the precursor is left unprotected the internal adduct 40 is formed instead. ... 

Unsaturated Dithioketene Acetals. The reaction of anion (1) with various o ,/3-unsaturated aldehydes and ketones occurs in a 1,2-fashion and provides vinyl thioketene acetals that are acceptable dienes for Diels-Alder reactions (eq 11) dienes of this type are difficult to access using other protocols. This method is also convenient for the introduction of a protected carbonyl group. 

Treatment of acrolein and cyclohexenone with 2-lithio-2-tri-methylsilyl-1.3-dithiane provides the corresponding unsaturated dithioketene acetals (eq 12). Subsequent exposure to w-butyl-lithium followed by Mel produces protected forms of a, 0-unsatu-rated ketones in almost quantitative yield anion addition occurs distal to the dithiane and alkylation takes place at the dithiane stabilized anion (eqs 13 and 14). Another interesting application is the use of suitably substituted 2-aryl-2-trimethylsily 1-1,3-dithianes as precursors for o-quinodimethanes (eq 15). ... 

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