3-Bromopropenyl Esters in Organic Synthesis:  Indium- and Zinc-Mediated Entries to Alk-1-ene-3,4-diols

Abstract

Metallic indium and zinc readily add to 3-bromopropenyl acetate (5) and benzoate (6) either in THF or in water, affording the corresponding 3-acyloxyallyl organometallic compounds. Nucleophilic addition to aldehydes opens a route to alk-1-ene-3,4-diols 2 in good to excellent yields. Two synthetic protocols were developed, the former involving indium in THF under Grignard conditions and the latter involving zinc in aqueous ammonium chloride under Barbier conditions. The diastereoselectivity, under all the conditions examined, mainly depends on the nature of the carbonyl compound; conjugated aldehydes afford syn adducts 2, while unconjugated aldehydes display the opposite anti stereopreference.

Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of 13C chemical shifts

“…Thus, plakilactone G ( 1 ) was converted to the corresponding 7,8- O -isopropylidene derivative by treatment with 2,2-dimethoxypropane and a catalytic amount of p -TsOH. As reported in the literature [29], the difference in the chemical shifts of the methyl groups in the five membered acetonide is larger for the cis -isomer (Δδ 0.12–0.14) when compared to the trans -isomer (Δδ 0.01–0.04). The observed Δδ value of 0.10 ppm between the two methyl groups in the plakilactone G acetonide (see Experimental) points towards the cis -isomer allowing us to suggest a 7,8- erythro relative stereochemistry.…”

Indium- and Zinc-Mediated Acyloxyallylation of Protected and Unprotected Aldotetroses—Revealing a Pronounced Diastereodivergence and a Fundamental Difference in the Performance of the Mediating Metal

“…Furthermore, according to the reported literature as well as our own experience, replacement of indium with cheaper zinc was unsuccessful in the acyloxyallylation of aldoses while it gave comparable results with standard aldehydes, a result not explained so far. 8 , 9 Thus, we set out to better understand the particular challenge of employing zinc in the case of carbohydrate starting materials ( Figure 1 , bottom right). We also decided to evaluate the corresponding 2 O ,3 O -isopropylidene protected derivatives in our survey, expecting to observe facial diastereodivergence, yielding the anti / anti -products ( ribo -type addition) ( Figure 1 , bottom left).…”

Allylation of Aldehyde and Imine Substrates with In Situ Generated Allylboronates – A Simple Route to Enatioenriched Homoallyl Alcohols

“…The NMR spectrum is identical with that reported in the literature. [41] Optical rotation: [α] D 20 = +19.7 (c = 0.23, CHCl 3 ) for 45 % ee. Determination of the configuration is based on the optical rotation data published [42] for (1S,2R)-(+)-1-phenylbut-3-ene-1,2-diol which was obtained by hydrolysis of (S)-5k.…”