Handbook of Functionalized Organometallics Applications in S

3.5 Synthesis and Reactions of Functionalized Allylic Boronates
available through traditional methods leading here to the anti-homoallylic alcohols
140 (Scheme 3.75).
O
B
R R
O
or R
catalyst 117
R R
R
O
B
O
139
= CH 2OAc, CH 2OTBS, CH 2OBn, CH 2Br, CH 2Cl
=
O
catalyst =
O
Scheme 3.75 Synthesis of functionalized allylic boronates by
cross-metathesis and their one-pot allylboration with aldehydes.
R
PhCHO
23 ºC
N N
Cl
Ru
Cl Ph
PCy3 117
R
OH
140: 63-75%
major anti
Synthesis of a series of novel functionalized achiral and chiral allyl boronates
has been recently reported by Ramachandran via nucleophilic SN 2¢-type addition
of copper boronate species (generated from the boronates 37, 141, 142 under
Miyaura conditions) [115,116] to various functionalized allyl acetates that were prepared
either via vinylalumination or by Baylis±Hillman reaction with various aldehydes
[117]. The resulting allylic boronates bearing an ester moiety (X = OR) were
subsequently used for the synthesis of a-alkylidene-b-substituted-c-butyrolactones
by allylboration of aldehydes (Scheme 3.76).
OAc O
R 2 X
R 1
O O
B B
O O
CuCl, LiCl, KOAc
DMF
O O
O
B B
B
O O
O
37 141
O
B
O
O
R2 X
R B 1
O
O
70-99%,E/Z>95%
R 1 =H,Me;R 2 = Ph, Me; X = OMe, OEt, OBn, OMenth, Me
EtO 2C
EtO 2C
Scheme 3.76 Allylic boronates via Hosomi±Miyaura borylation.
O O
B B
O O
142
CO 2Et
CO 2Et
Palladium-catalyzed cross-coupling of alkenyl stannanes with pinanediol bromomethyl
boronate (143) has been reported to give homologous allylic boronates
89