A Practical Radical Based Access to Functionalised Geminal Bisphosphonates
作者:Samir Z. Zard、Fabien Gagosz
DOI:10.1055/s-2003-37108
日期:——
Xanthate derivatives of tetraalkylmethylenebisphosphonate add efficiently to various functionalised olefins to give the corresponding adducts via a radical chain reaction initiated by a small amount of lauroyl peroxide.
Substrate-Controlled Highly Diastereoselective Synthesis of Primary and Secondary Diorganozinc Reagents by a Hydroboration/Boron–Zinc Exchange Sequence
作者:Eike Hupe、M. Isabel Calaza、Paul Knochel
DOI:10.1002/chem.200204662
日期:2003.6.16
The scope of substrate-controlleddiastereoselectivehydroborations can be considerably enhanced by a boron-zincexchange reaction, providing organozinc derivatives that react with a broad range of electrophiles. Even normally unreactive boronic esters, obtained by Rh-catalyzed hydroboration with catecholborane, react readily with iPr2Zn providing the corresponding zinc reagents in high diastereoselectivity
Diastereoselective synthesis and reactions of diorganozinc reagents obtained after hydroborations with 9-BBN-H, thexylborane and catecholborane
作者:Eike Hupe、M.Isabel Calaza、Paul Knochel
DOI:10.1016/s0040-4039(01)01916-5
日期:2001.12
greatly enhanced by a boron–zinc exchange reaction, providing organozincs that react with a broad range of electrophiles. Diastereomerically enriched diorganozincs can be obtained after hydroborations with 9-BBN-H, thexylborane and catecholborane.
Synthetic equivalents of alkynyl and propargyl radicals
作者:Peter Boutillier、Samir Z. Zard
DOI:10.1039/b101751i
日期:——
Radicals derived from β-ketoesters can, depending on the
position of the unpaired electron, represent synthetic equivalents to the
high energy and elusive alkynyl radicals or to the stabilised and
relatively unreactive propargyl radicals by application of the xanthate
transfer reaction followed by nitrosative cleavage of the corresponding
isoxazolinones.
An improved process for the metathesis of alkenyl esters utilizing substantially reduced catalyst levels is provided. For the process, an alkenyl ester of the formula ##STR1## where R is hydrogen or alkyl, R* is tertiary alkyl or an aromatic group, and n is an integer from 2 to 20 is reacted with a tungsten hexachloride/tetraalkyltin catalyst.