Reactivity of allylic dimetallic zinc reagents. 1

Abstract

H, 5.85. Found C, 73.54; H, 5.81.3,a-Dimet how-7-p hen y 1-1 1 -oxatricyclo[ 7.3.0.01~o]dodeca-2,4,8-trien-lO-one (13). A solution of 10 (1.59 g, 4.7 m o l ) in dichloroethane (25 mL) was added dropwiee to a stirred solution of rhodium(II) odanoate (0.035 g, 0.047 m o l ) in dichloroethane (25 mL) heated under reflux in an argon atmosphere. After being heated for an additional 12 h, the solvent was removed under reduced pressure and the residue was recrystallized from hexane to give 13 as a colorless solid 0.35 g, 17% yield; mp 126130 "C; IR (CCl,) 1765,1605 cm"; ' H NMR (CDClJ 6 7.37-7.15 (m, 5 H), 6.78 (d, 1 H, J = 1.7 Hz), 4.91 (e, 1 H), 4.72 (d, 1 H, J = 6.7 Hz), 4.34(d,lH,J=8.7Hz),4.29(dd,lH,J=9.3,1.7Hz),4.14 (d, 1 H, J = 8.7Allylic 1,l-dimetaUic species 2, prepared in situ from the propargylic ether 1, are multicoupling reagents. They were allowed to react in a one-pot reaction, with a large variety of electrophiles $-carbonyl compounds (acyl chlorides, aldehydes, ketones, phenyl isocyanate, methyl chloroformate), alkyl bromides, and an amino ether-and then E,-acidic water, iodine, aryl or vinyl iodide in the presence of palladium(0). The isolated yields, based on 1 (5 steps), are fair to good in most cases. The fiist attack (E,) always occurs on the carbon atom a to the oxygen; the second attack (E,) is regio-and stereoselective on the carbon atom a to the TMS moiety.

Preparation of γ-Heterosubstituted Allylindium and Diindium Reagents and Their Reactions with Carbonyl Compounds

“…The difficulty encountered in the displacement of the indium atom with electrophiles such as chlorostannane and iodine may come from this intramolecular coordination. The coordination of the alkoxide oxygen to the vinylic indium in the homoallylic alkoxide would prevent the attack of the electrophiles as was observed in a vinylzinc case 4

5

6

…”

Total Synthesis of Bafilomycin V1: A Methanolysis Product of the Macrolide Bafilomycin C2

“…At the time, there were no methods for the formation of enantioenriched methoxy-substituted allenylmetal reagents , Following this procedure, we prepared the allenylzinc reagent from TMS-propargyl methyl ether, which was allowed to react with a model aldehyde, 37 , affording a 47:47:6 inseparable mixture of diastereomers in high yield (eq 3). As these additions are known to occur through a cyclic transition state, the major isomers are presumed to be the anti adducts and the minor is presumed to be a syn isomer.…”

Carbozincation Reactions of Carbon–Carbon Multiple Bonds

“…The latter can also react with other electrophiles, such as acyl chlorides, ketones, aldehydes, phenyl isocyanate, alkyl halides, and imines to give the corresponding monofunctionalized vinyl metals. 159 These intermediates can then react with a second electrophile. The reactivity of the second metal is lower than the reactivity of the first due to the vinylic character of the remaining metal and the intramolecular coordination by the heteroatom.…”