A highly effective one-pot bicycloannulation methodology for the synthesis of berban and yohimban systems based on organotin-mediated three-component coupling (N-acylative pentadienylation of C:N bonds)
摘要:
A highly effective bicycloannulation methodology for the synthesis of berban and yohimban alkaloid systems is described. Three-component coupling reactions of 2,4-pentadienyltin reagents with C=N bonds and alpha,beta-unsaturated acyl chlorides furnish bicycloannulated products in a one-pot operation. For example, the reactions of 2,4-pentadienyltributyltin (1) with isoquinoline derivatives activated by acryloyl chloride afford the tetracyclic (+/-)-allo-berban systems stereoselectively. Similarly, the reaction of 1 with 3,4-dihydro-beta-carboline (11) gives the pentacyclic (+/-)-allo-yohimban system. The reaction is not affected by the stereochemistry of the 2,4-pentadienyltin reagent. A new substituted 2,4-pentadienyltin reagent, 3-(hydroxymethyl)-2,4-pentadienyltrimethyltin (19), is prepared via 3-(hydroxymethyl)pentadienyl dianion. The three-component coupling reaction of 19 with 11 and acryloyl chloride affords the (+/-)-allo-16-(hydroxymethyl)yohimban system, from which (+/-)-nitraraine is readily synthesized. In addition, 1,3-asymmetric induction leads to the high diastereoselectivity realized in bicycloannulation (up to 94% de) when (S)-3-[(tert-butyldimethylsiloxy)methyl]-3,4-dihydroisoquinoline (27), which is readily derived from L-phenylalanine, is used in the three-component coupling reaction.
Enantioselective deprotonation of 4-tert-butylcyclohexanone by conformationally constrained chiral lithium amide bases
作者:Varinder K. Aggarwal、Paul S. Humphries、Ashley Fenwick
DOI:10.1039/a905947d
日期:——
Conformationally rigid chirallithium amides based on a tetrahydroisoquinoline motif have been prepared bearing a range of substituents at C1 and C3. These bases were tested in the asymmetricdeprotonation reaction of 4-tert-butylcyclohexanone. Although the 1-substituted tetrahydroisoquinolines gave low enantioselectivity, the chiralbases containing a nitrogen heterocycle at C3 were found to induce
Intermolecular Regio‐ and Stereoselective Hetero‐[5+2] Cycloaddition of Oxidopyrylium Ylides and Cyclic Imines
作者:Changgui Zhao、Daniel A. Glazier、Daoshan Yang、Dan Yin、IIia A. Guzei、Michael M. Aristov、Peng Liu、Weiping Tang
DOI:10.1002/anie.201811896
日期:2019.1.14
We have developed the first intermolecular hetero‐[5+2] cycloaddition reaction between oxidopyrylium ylides and cyclic imines with excellent control of regio‐ and stereoselectivity. Surprisingly, divergent stereochemistry was observed depending on the substitution pattern of the oxidopyrylium ylide. This new reaction provides quick access to highly substituted nitrogen‐containing seven‐membered rings—azepanes
Nucleophilic addition reactions of allylic tin reagents to chiral 3-substituted 3,4-dihydroisoquinolines activated by acyl chlorides afford anti 1,3-disubstituted 1,2,3,4-tetrahydroisoquinolines stereoselectively through high 1,3-asymmetric induction.