Phosphonates, allylic, coupling reactions

An alternative allylic coupling has been reported (J. Am. Chem. Soc. 2004,126, 10676 and 11130) by Amir Hoveda of Boston College. Coupling of the allylic phosphonate 8 with diethyl zinc in the presence of an enantiomerically-pure Cu catalyst gives the branched product 9 in 95% . It is striking that the reaction works almost as well with the allylic phosphonate 10. Reaction with diethyl zinc in the presence of the enantiomerically-pure Cu catalyst forms the quaternary center ofl 1 in 91 % . 

Kazmaier and Jena have presented syntheses of stannylated, allyl (86) and vinylphosphonates (87) by molybdenum-catalyzed hydrostannation of the corresponding propargyl- (84) and alkynylphosphonate (85) derivatives (Scheme 27). " The stannylated phosphonates, obtained with high regios-electivities, were applied as building blocks in further modifications, such as Pd-catalyzed cross coupling reactions or iodination. 

Starting from L-ascorbic acid, a chiral building block from nature, 2,3-isopro-pylidene-L-glyceraldehide 21 was obtained and subjected to an il-selective Homer-Wadsworth-Emmons-type reaction [38] with phosphonate 22 to give -alkene 23. Two-step manipulation of the diol unit in 23 afforded 24 which underwent y-allylic coupling to (R)-25 with 97% e.e. and 77% yield. In the last three steps, cyclic ketone (45)-4 was obtained, with approximately 65% yield. This can be converted to sertraline by one of the routes described above. 

The synthesis of j3-elemene outlined below6 is also based on the coupling of 1,10-dibromo-2,8-decadienes under influence of nickel carbonyl. The key allylic dibromide (B) has been built up from the unsaturated ester (A) utilizing a Claisen rearrangement and two successive phosphonate Wittig reactions. ... 

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