Marshall-Tamaru reaction

Scheme 5-13. Mechanism rationale of the Marshall-Tamaru reaction.

The efficiency of the Marshall-Tamaru reaction was demonstrated toward the synthesis of several natural products. " An efficient total synthesis of cruentaren A, a polyketide with a 12-membered macrolactone ring, was achieved featuring a Marshall-Tamaru reaction as the key step (Scheme 5-14)J ... 

Scheme 5-14. The Marshall-Tamaru reaction as the key step for the synthesis...

The addition of a chiral allenyl metal to an aldehyde generating a 2-substituted butynyl structure is named Marshall-Tamaru MT) reaction (Scheme 5-13). An allenyl palladium species is generated via a formal Sn2 substitution of the mesylate, which in turn undergoes a transmetalation with diethylzinc yielding a nucleophilic species (Scheme 5-13). The reaction of the electrophile proceeds via a similar -ester enolate transition state as depicted in Scheme 5-13. Corresponding allenylindium reagents can also be used instead of allenylzinc intermediates. ... 

In an extension of the methodology reported by Tamaru and coworkers for allylic benzoates16, Marshall and Adams found that propargylic mesylates could be converted to allenylzinc reagents with Pd(0) catalysts and an equivalent of Et2Zn17,18. When this novel palladiozincation reaction was conducted in the presence of aldehydes, anti homopropar-gylic alcohols were produced as the major adducts (Tables 14 and 15). 

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