Organic synthesis using haloboration reaction XVIII. A stereoselective synthesis of β—mono- and β,β-disubstituted α,β-unsaturated esters

Haloboration: scope, mechanism and utility

“…[69][70][71] During their fundamental studies, Lappert et al used esterification of R-BX 2 with catechol or alkanols to transform their products into stable and conveniently analysed derivatives. 12,37 Esterification by ether cleavage 72 or by reaction with the respective alcohol 73 gave boronic esters with prolonged shelf-life. 25 Other functionalisation includes formation of R-B(dan) (dan = 1,8-diaminonaphthalen-N,N 0diyl), 74 R-B(MIDA) complexes (MIDA = N-Methyliminodiacetate), 75 or R-BF 3 K salts.…”

A New and Practical Synthesis of α-Amino Acids from Alkenyl Boronic Acids

“…In addition to boronic acids with various substitution patterns the reaction also works with boronate derivatives (entry 9). Of special interest is the participation of bromo-substituted derivatives ( 1b and 1c ) to form bromoalkenyl amino acids (entries 8 and 9). Compounds of this type were postulated to be “Trojan horse” inhibitors 4c,5m by generating highly reactive allenic intermediates upon their exposure to the appropriate enzymes.…”

Cascade Radical Cyclizations via Biradicals Generated from (Z)-1,2,4-Heptatrien-6-ynes

“…Enyne−allene 4 was again synthesized by this new procedure in order to determine whether this synthetic method will tolerate the presence of additional carbon−carbon double bonds. Treatment of 1-hexen-5-yne ( 9 ) with BBr 3 followed by esterification with isopropyl alcohol furnished the corresponding ( Z )-alkenylboronic ester 10 in 58% isolated yield. The presence of a terminal carbon−carbon double bond in 9 did not appear to interfere with bromoboration.…”