The Use of Vicinal Twofold Heck Reaction Products in Diastereoselective Sequential Michael Additions — A Convenient Access to Enantiomerically Pure Six‐Ring Anellated Cispentacin Derivatives

The palladium-catalyzed coupling reactions of various acrylic acid derivatives 2a–e (e.g. methyl, tert-butyl, benzyl, menthyl esters) with 1,2-dibromobenzene (1), 1,2,3-tribromobenzene (4) and 1,2-dibromocyclohexene (6) yielded the correspondingly substituted ortho-diethenylarenes 3a–e, 1,2,3-triethenylarenes 5a,b and (E,E)-1,3,5-hexatriene derivatives 7a,b. Some of these vicinal diacrylates (3a–d, 5b, 7a,b) were converted to 1,2,3-trisubstituted indane- and tetrahydroindane derivatives 10a–d, 15a,b, 18, 20, 23, and 12a,b, 16b by domino conjugate addition of nitrogen, carbon, and sulfur nucleophiles. With benzyl(trimethylsilyl)amine (9) as an ammonia equivalent, the relative configuration of all three newly formed stereogenic centers was controlled (d.e. >90%). Therefore, with chiral non-racemic ammonia equivalents like benzyl[(S)-phenylethyl]amine (14) and TMS-(R)-AMP (17), protected diastereomerically pure β-amino esters were obtained, which could easily be deprotected by standard methods to yield the enantiomerically pure β-amino acids 27 and 28.