22885-64-9Relevant articles and documents
Lithium bis(ethylenedioxyboryl)methide and its reactions with carbonyl compounds and with the chlorotriphenyl derivatives of germanium, tin and lead
Matteson, Donald S.,Jesthi, Pradipta K.
, p. 25 - 37 (2007/10/05)
Transesterification of tris(dimethoxyboryl)methane, HC[B(OCH3)2]3, with ethylene glycol yielded tris(ethylenedioxyboryl)methane (I), HC(BO2C2H4)3 which with methyllithium in THF at -70°C precipitated lithium bis(ethylenedioxyboryl)methide (II), Li+ HC(BO2C2H4)2-. Reaction of II with Ph3MCl, where M = Ge, Sn, or Pb, gave Ph3MCH(BO2C2H4)2. The analogous 1,3-propanediol ester, Li+HC(BO2C3H6)2-, yielded Ph3MCH(BO2C3H6)2. Treatment of Ph3SnCH(BO2C2H4)2 with MeLi followed by Ph3SnCl gave (Ph3Sn)2CHBO2C2H4, showing that one B and one Sn atom are sufficient to stabilize a carbanion. Reaction of II with aldehydes gave high yields of 1-alkene-1-boronic esters, RCHCHBO2C2H4, with unexpectedly high stereoselectivity, 90-100% trans by NMR analysis. Aqueous work-up of these boronic esters yielded the boronic acids, RCHCHB (OH)2, which crystallized as the pure trans isomers. Ketones react with II in an analogous manner. The reaction with acetophenone was not stereospecific. Functional group compatibility has been demonstrated in condensations of II with 1,3-dichloroacetone, cinnamaldehyde, p-nitrobenzaldehyde, and p-dimethylaminobenzaldehyde. The trans geometry of the major isomer of CH3CHCHBO2C2H4 was proved by B-butylation with butyllithium followed by rearrangement with iodine and base to form cis-2-heptene, a sequence of known stereochemistry, and analogous structure proofs were carried out with cis-CH3CHCHBO2C2H4 and trans-C6H5CHCHBO2C2H4.
