Samarium(II) iodide: A diastereoselective reagent for the synthesis of aromatic 1,2‐diol structures — model reactions

Abstract

Variation of the reaction conditions for the C-C coupling reaction of aromatic carbonyl compounds to their 1,2-diol structures in the presence of samaraium(I1)-iodide led to different diastereoselectivities. The molar ratio of the starting materials, substituents, and solvent variation had a significant influence on 1,2-diol formation. An interpretation of the observed results is suggested. Sterical demands ofthe active complex and an intramolecular samarium-oxygen interaction could lead to the diastereomer ratio obtained.

Synthesis of OH-functionalized poly(p-xylylene)s by reductive coupling polymerization of aromatic dialdehydes with stoichiometric amounts of divalent samarium compounds

“…Reactions of compounds 1 in the presence of SmBr 2 were performed in order to optimize reaction parameters and study possible side reactions (Scheme 2). The yields of the corresponding hydrobenzoins were almost quantitative (2 a: 95%; 2b: 98%), no side products were observed which corresponds well to previous results obtained with SmI 2 as coupling agent [8].…”

“…The stereochemistry of Sm(II) assisted couplings of monocarbonyl compounds has been discussed before in detail with respect to the formation of hydrobenzoin meso/ dl hydrobenzoin [8]. When SmBr 2 has been used here as coupling agent a ratio of meso/dl hydrobenzoin of 48/52 has been observed with 1 a.…”

“…The coupling takes place by radical recombination, which should result in case of aromatic dicarbonyl compounds in OH-PPXs. In spite of the radical character of the intermediates control of the stereochemistry of this coupling reaction is possible to a certain extent as shown previously [8]. Based on the results mentioned above a new approach has been developed for the synthesis of OH-PPX by the reductive coupling of aromatic dialdehydes with SmI 2 [9,10].…”

SmI2 as a Reagent in Polymer Chemistry

“…The analogous homocoupling polymerization of aromatic dialdehydes produces poly(1,2-diol)s with moderate molecular weight. [24] Poly(alcohol)s with a tertiary alcohol moiety in the main chain are accessible by the cross-coupling polymerization of diketones with bifunctional unsaturated compounds (Scheme 8). [25] The present polymerization as hydrophilic materials, the unavoidable oxidation of secondary alcohol units often causes serious problems in practical use.…”

Synthesis of OH-functionalized poly(p-xylylene)s by reductive coupling polymerization of aromatic dialdehydes with stoichiometric amounts of divalent samarium compounds

“…The coupling takes place by radical recombination, which should result in case of aromatic dicarbonyl compounds in OH-PPXs. In spite of the radical character of the intermediates control of the stereochemistry of this coupling reaction is possible to a certain extent as shown previously [8]. Based on the results mentioned above a new approach has been developed for the synthesis of OH-PPX by the reductive coupling of aromatic dialdehydes with SmI 2 [9,10].…”