The Stereochemistry of Organometallic Compounds. XXXIII. Preparation and Reactions of Some Substituted Buta-1,3-Dienes

Abstract

Hydroformylation and hydrocyanation of 2-methylhex-1-en-3-yne surprisingly both involve addition to the alkyne leading to the formation of formyl- and cyano-buta-1,3-dienes whose reactivity in Diels-Alder and ene-type reactions has been investigated.

Regioselective Hydroformylation of Enynes Catalyzed by a Zwitterionic Rhodium Complex and Triphenyl Phosphite

“…h A cyclopentenone was identified by an olefin 1 H NMR signal at 5.90 ppm in the crude mixture, it had a ratio of 1:2 to 4a . Campi and Jackson identified this proton signal as being due to the cyclopentenone 5c…”

“…The Hidai group described the hydroformylation of the conjugated enyne ( Z )-1,4-diphenyl-1-buten-3-yne to form (2 E ,4 Z )-2,5-diphenyl-2,4-pentadienal as the exclusive hydroformylation product in 80% conversion and 39% isolated yield. Doyama and others 5a,b noted that when an alkyne is conjugated to an alkene, the triple bond is more reactive toward hydroformylation. Conjugated enynes undergo hydroformylation giving formyl dienes in either a linear or branched fashion.…”

The First Regioselective Hydroformylation of Acetylenic Thiophenes Catalyzed by a Zwitterionic Rhodium Complex and Triphenyl Phosphite

“…This study suggested the possibility of a sulfur assisted hydroformylation of acetylenic thiophenes. In many studies, including our own work on the hydroformylation of enynes, it was observed that when there is both a double bond and a triple bond present within a molecule, the triple bond is more reactive. This is consistent with the binding energy for rhodium−triple bond coordination being lower than the binding energy for the metal coordinating to a double bond.…”

Ligand-Controlled Regiodivergent Nickel-Catalyzed Hydrocyanation of Silyl-Substituted 1,3-Diynes

“…In sharp contrast to the hydrocyanation of alkynes, the hydrocyanation of 1,3-diynes still remains elusive in the literature due to the intractable challenges in regio- and stereoselectivity control for unsymmetrical internal alkynes. Until now, only a limited number of special unsymmetrical internal alkynes have been hydrocyanated with high regio- and stereoselectivity . Obviously, the hydrofunctionalization of unsymmetrical 1-aryl-4-silyl-1,3-diynes would pose extra difficulties in regard to monoalkynes: (a) Regioselectivity between two alkyne motifs (Scheme a, A); ,, (b) regioselectivity in each migratory insertion (Scheme a, B), (c) selectivity between mono- and dihydrofunctionalization (Scheme a, C), and (d) stereoselectivity in each migratory insertion (Scheme a, D).…”