Reactifs de grignard vinyliques γ fonctionnels

Allenyl Azide Cycloaddition Chemistry. 2,3-Cyclopentennelated Indole Synthesis through Indolidene Intermediates

“…A solution of ( Z )-3-Iodo-2-phenyl-prop-2-en-1-ol ( 58a )25 (1.12 g, 4.31 mmol) in 160 mL of CH 3 CN was irradiated at 254 nm for 2 h and then concentrated under reduced pressure. 1 H NMR analysis of the reaction mixture indicated that it contained a 5: 1 mixture of the E and Z isomers, respectively.…”

A multicomponent coupling strategy suitable for the synthesis of the triene component of the oxazolomycin antibioticsThis is one of a number of contributions from the current members of the Dyson Perrins Laboratory to mark the end of almost 90 years of organic chemistry research in that building, as all its current academic staff move across South Parks Road to a new purpose-built laboratory.

“…It was decided to adopt a strategy involving coupling between the previously prepared isomeric vinyl halides 2a,b and stannane 27 as the key step (Scheme 8); the latter would be derived from the known iodide 28. 53 Although (Z )-iodide 2a had been prepared previously as a 94 : 6 mixture of 1(Z ) : 1(E )-isomers via a (Z )-selective Wittig olefination (vide supra), it was envisaged that separation of this isomeric mixture after the Stille reaction would be particularly troublesome, if not impossible, and so an alternative synthesis of the (Z )-halide which would deliver the product with greater stereoisomeric purity was desirable. To this end, conversion of aldehyde 4 to dibromide 29 followed by stereoselective palladium-catalysed monoreduction according to the recent literature protocol 54 gave vinyl bromide 30 in good yield (76%) and, crucially, as an excellent 99 : 1 mixture of 1(Z ) : 1(E )isomers (Scheme 9).…”

Progress in the total synthesis of inthomycins

“…Aldehyde 35 was then converted into dibromide 37 using PPh 3 /CBr 4 followed by stereoselective palladium-catalyzed monoreduction according to the literature available protocol [ 41 ] to give vinyl bromide 38 in 76% yield ( Z / E as 99:1 mixture). Iodide 15a [ 42 ] was prepared stereoselectively from propargyl alcohol following the literature procedure, and the free hydroxy group was then protected as its TBDMS ether to produce 39 in 99% yield.…”

“…Deprotection of the TBDMS ether of stannane 40 with tetra-n-butylammonium fluoride (TBAF) in THF and then subsequent Swern oxidation of the crude alcohol gave aldehyde 41 in 71% yield. The aldehyde 41 was treated with ethyl isobutyrate (42) in the presence of LDA to afford the aldol adduct (Z)-(rac)-43 in the racemic form (92% yield). The stannane (Z)-(rac)-43 was then subjected to Stille coupling with iodide (E,E)-36b (3:1 mixture of stereoisomers, 3 equiv) using Pd(CH 3 CN) 2 Cl 2 /DMF conditions to produce a 3:1 mixture of (Z,Z,E):(Z,E,E) triene products (rac)-12a and (rac)-12c in 72% yield after 10 h reaction time.…”