Enantioselective Synthesis of Planar-Chiral 1,n-Dioxa[n]paracyclophanes via Catalytic Asymmetric ortho-Lithiation
摘要:
Highly enantioselective ortho-lithiation and dilithiation of 1,n-dioxa[n]paracyclophanes were realized with the use of see-butyllithium and a catalytic or stoichiometric amount of sparteine. Quenching with various electrophiles, such as iodine, iodomethane, and chlorodiphenylphosphine, afforded chiral mono- and disubstituted paracyclophanes with good to excellent ee.
1,n-dioxa[n]paracyclophanes possessing a phenolic hydroxylgroup have been synthesized via enantioselective ortho-lithiation. Subsequent reaction with 2,2′-biarylene phosphorochloridites gave a new family of chiral phosphites. These phosphites were then used as chiral ligands in the enantioselective palladium-catalyzed allylic alkylation of dimethyl malonate with (E)-1,3-diphenylallyl acetate and the
摘要 通过对映选择性邻位锂化合成了具有酚羟基的各种平面手性1,n-二氧杂[ n ]对环环烷酮。随后与2,2'-亚芳基次氯代磷酸酯的反应产生了新的手性亚磷酸酯族。然后将这些亚磷酸酯用作丙二酸二甲酯的对映体选择性钯催化的烯丙基烷基化与(E)-1,3-二苯基烯丙基乙酸酯的手性配体,以及铑催化的苯基硼酸的1,4-加成到环己-2-烯酮中的手性配体。 通过对映选择性邻位锂化合成了具有酚羟基的各种平面手性1,n-二氧杂[ n ]对环环烷酮。随后与2,2'-亚芳基次氯代磷酸酯的反应产生了新的手性亚磷酸酯族。然后将这些亚磷酸酯用作丙二酸二甲酯的对映体选择性钯催化的烯丙基烷基化与(E)-1,3-二苯基烯丙基乙酸酯的手性配体,以及铑催化的苯基硼酸的1,4-加成到环己-2-烯酮中的手性配体。
Kinetic Resolution of Ansa Cyclophanes by Peptide-Catalyzed Aldol/Retro-Aldol Reactions
Peptide‐catalyzed aldol and retro‐aldol reactions were applied to kineticresolution of planar‐chiral ansa cyclophanes. By performing these reactions sequentially with the enantiopair of resin‐supported tripeptides, the aldol product could be obtained in a good enantiopurity.
The asymmetric induction of planar chirality in 1,n-dioxa[n]paracyclophane derivatives via asymmetric ortho-lithiation is described. Enantioselective ortho-lithiation of unflippable 1,n-dioxa[n]paracyclophanes (n <= 11) using sec-BuLi-(-)-sparteine at -78 degrees C and subsequent treatment with electrophiles gave the corresponding planar-chiral monosubstituted paracyclophanes with excellent ee. Further lithiation of these compounds and treatment with electrophiles gave planar-chiral paracyclophanes with two different substituents. Dilithiation of unflippable 1,n-dioxa[n]paracyclophanes gave the corresponding C(2)symmetrical disubstituted products with almost perfect ee. In the case of flippable 1,n-dioxa[n]paracyclophanes (n >= 12), a stepwise reaction was required for the highly enantioselective formation of disubstituted products. (C) 2011 Elsevier Ltd. All rights reserved.