Eschenmoser fragmentation reaction Subject

During modei studies for the synthesis of botrydiane sesquiterpene antibiotics, B.M. Trost and co-workers prepared a compiex 1,6-enyne precursor for transition metal catalyzed enyne metathesis reactions. The 1,6-enyne was prepared from a heavily substituted alkynal, which was synthesized via the Eschenmoser-Tanabe fragmentation of an epoxy ketone. The resulting alkynal was unstable, so it was immediately subjected to a Wittig oiefination to afford the desired 1,6-enyne. 

A(, -Dimethyl(methylene)iminium salts have been the most widely used class of preformed iminium salts, mainly due to their applications in the synthesis of a,p-unsaturated carbonyl compounds, normally accomplished by subjecting the /V, -dimethyl Mannich base to quatemarization followed by base-induced elimination. Table 3 outlines various counterion forms of /V, -dimethyl(methylene)iminium salts that have been used in Mannich reactions as well as their synthetic precursors. The crystalline iodide (30), known also as Eschenmoser s salt , has seen the most widespread use and is prepared by thermal fragmentation of (iodomethyl)trimethylammonium iodide or, more conveniently, by a variant of the... 

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See also in sourсe #XX -- [ ]

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