The Use of Phosphine Ligands to Control the Regiochemistry of Pd-Catalyzed Hydrostannations of 1-Alkynes:  Synthesis of (E)-1-Tributylstannyl-1-alkenes

Abstract

The regiochemistry of palladium-catalyzed hydrostannations of terminal alkynes is dramatically influenced by ligand effects. Use of phosphines such as Cy3P, t-Bu2PCH2t-Bu, and t-Bu3P provides (E)-1-tributylstannyl-1-alkenes with regioselectivities up to >99:<1 for substrates where the commonly used Ph3P shows much lower regioselectivities.

Synthesis of cyclooxygenase metabolites of 8,9-epoxyeicosatrienoic acid (EET): 11- and 15-hydroxy 8,9-EETs

“…The NMR analysis of the major product after purification by HPLC revealed it to be the trans - trans isomer 10 (Scheme 3) rather than the desired trans - cis product 9 . Complex mixture of products obtained in this reaction is an indicator of poor regio- and stereoselectivity of the first hydrostannylation step, which can be improved by using alternative reaction conditions such as described by Darwish et al 32 Poor reaction yield on the other hand can be improved by using copper-based catalytic systems, 33 which revealed to be superior to palladium based catalysts in multiple cases. Thus hydrostannylation of 3 under Darwish conditions followed by CuTC mediated Stille coupling provided diastereomeric mixture of EHET methyl esters 9 in 47 % yield for two steps.…”

Total Synthesis Confirms the Molecular Structure Proposed for Oxidized Levuglandin D2

“…(E)-tert-butyldimethyl((1-(tributylstannyl)oct-1-en-3-yl)oxy)silane ( 5 ) was prepared as described previously. 41 …”

Bis(1,1-dimethylethyl)(2,2-dimethylpropyl)phosphine

“…The catalyst derived from DTBNpP and Pd 2 (dba) 3 was shown to be effective for the hydrostannylation of terminal alkynes. 11 The DTBNpP catalyst system gave a 70 % yield and a 96:4 ratio of the 1-stannyl-and 2-stannylalkyne products (eq 7). The regioselectivity was comparable to that obtained with tricyclohexylphosphine or TTBP.…”