Novel Extension of Meyers' Methodology: Stereoselective Construction of Axially Chiral 7,5-Fused Bicyclic Lactams
摘要:
A novel extension of Meyer's lactamization is reported for the preparation of seven-membered ring lactams 1a-d incorporating a biaryl unit. The required keto-esters 2a-c were readily accessible via the Suzuki coupling reaction. A borylation-Suzuki coupling (BSC) sequence was successfully developed for the high-yielding preparation of keto-ester 2d. Cyclization of the resulting keto-esters 2a-d or keto-acids 5a,c,d in the presence of (R)-phenylglycinol afforded the desired lactams 1a-d in high yields (72-93%) and excellent diastereoselectivities (>95%). This methodology provides a facile stereoselective access to new axially chiral bridged biaryls.
Highly atroposelective Meyers' lactamization promoted by pivalic acid under microwave irradiation is reported which allows the construction of nonracemic substituted-dibenzo(di)azepine derivatives through a center to axial chirality transfer principle, controlling the otherwise configurationally labile biaryl axis. This approach provides a straightforward entry to enantioenriched analogues of biorelevant architectures.
Novel Extension of Meyers' Methodology: Stereoselective Construction of Axially Chiral 7,5-Fused Bicyclic Lactams
作者:Maël Penhoat、Vincent Levacher、Georges Dupas
DOI:10.1021/jo035195i
日期:2003.11.1
A novel extension of Meyer's lactamization is reported for the preparation of seven-membered ring lactams 1a-d incorporating a biaryl unit. The required keto-esters 2a-c were readily accessible via the Suzuki coupling reaction. A borylation-Suzuki coupling (BSC) sequence was successfully developed for the high-yielding preparation of keto-ester 2d. Cyclization of the resulting keto-esters 2a-d or keto-acids 5a,c,d in the presence of (R)-phenylglycinol afforded the desired lactams 1a-d in high yields (72-93%) and excellent diastereoselectivities (>95%). This methodology provides a facile stereoselective access to new axially chiral bridged biaryls.
Enantioselective Route to 5-Methyl- and 5,7-Dimethyl-6,7-dihydro-5<i>H</i>-dibenz[<i>c</i>,<i>e</i>]azepine: Secondary Amines with Switchable Axial Chirality
作者:Silvain L. Pira、Timothy W. Wallace、Jonathan P. Graham
DOI:10.1021/ol900333c
日期:2009.4.2
featuring an axis-center stereochemicalrelay, was prepared enantioselectively from 2′-acetylbiphenyl-2-carboxylic acid, using (R)-2-phenylglycinol as an auxiliary for the control of both elements of chirality. The biarylaxis in 4 preferentially adopts the aS-configuration, with the methyl substituent pseudoequatorial, but conversion into the corresponding N-Boc derivative locks the axis into the aR-configuration