Sufinic acid

In the following examples, sulfur dioxide and benzenesulfenic acid (benzene-sufinic acid) are simultaneously extruded from the initial adducts. In this way, a series of highly congested benzene derivatives, which are otherwise difficult to prepare, were synthesized in good overall yields (Scheme 33) [39,40,159,160]. 

As a related reaction, hydrosulfination of propylene with SO2 and H2 gives alkane sufinic acid 21, which is unstable and trapped in situ by Michael addition to a,-unsaturated ketones such as mesityl oxide (22), and the y-oxo sulfone 23 is isolated in high yields. The hydrosulfination proceeds in CH2CI2 using DPPP as a ligand [13]. 

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