Mercurilactonization reductive demercuration

Another example is mercurilactonization, which proceeds with good stereocontrol in the formation of both y- and 8-lactones, but suffers from elimination during the reductive demercuration. An exploration of a number of reagents and conditions, including NaBH and various pHs, hydrogen over Wilkinson s catalyst, Bu3SnH and NaaS, indicates that reductive elimination is minimized in alkali borohydride, although it cannot be avoided entirely (Scheme 28). ... 

However, a limitation in the use of certain thiol reagents, as for most reagents used for demercuration, can be their propensity to undergo elimination with reversion to the starting material. Sodium sulfide, for example, cannot be used in the reduction step of the mercurilactonization (Scheme 28), and the presence of a base (NaHCOs or EtsN) is necessary in the 1,3-propanedithiol reduction of mercurials. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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