220156-28-5

Upstream product

• 18871-66-4 N,N-dimethylacetamide dimethyl acetal 
• 251956-33-9 (4R,5R)-2-[(E)-2-{hydroxymethyl}ethenyl]-4,5-bis[methoxy(diphenyl)methyl]-1,3,2-dioxaborolane 
• 199185-13-2 (4R,5R)-4,5-Bis-(methoxy-diphenyl-methyl)-2-((1S,2S)-2-pentyl-cyclopropyl)-[1,3,2]dioxaborolane 
• 199185-03-0 (4R,5R)-2-((E)-Hept-1-enyl)-4,5-bis-(methoxy-diphenyl-methyl)-[1,3,2]dioxaborolane 
• 130888-43-6 (4R,5R)-4,5-bis(methoxymethyl)-2-(p-methoxyphenyl)-α,α,α',α'-tetraphenyl-1,3-dioxolane 
• 130874-89-4 (2R,3R)-1,4-dimethoxy-1,1,4,4-tetraphenyl-2,3-butandiol 
• 220156-18-3 (4R,5R)-4,5-Bis-(methoxy-diphenyl-methyl)-[1,3,2]dioxaborolane 

Relevant academic research and scientific papers

Diastereo- and enantiomerically pure allylboronates: Their synthesis and scope

Allylboronates are highly attractive reagents for allyl additions. Enantiomerically pure, stable reagents with a stereogenic centre in a-position to boron are especially versatile, albeit often difficult to synthesize. Starting from boron-containing allyl alcohols 6 and 7, which are discussed in detail herein, a set of reagents were obtained via [3,3]-sigmatropic rearrangements and consecutive transformations in the side chain. The configurations could be established first by chemical correlation, but also by X-ray crystallography (16, 18, 34, and 39). Allyl additions were performed resulting in the formation of predominantly (Z)-configured homoallylic alcohols (31, 43-45) with high enantiomeric excess. Detailed investigations on the matched-mismatched interaction between the reagents 15/16 (and ent-15/ent-16, respectively) and isopropylidene glyceraldehyde 42 d are presented.

Synthesis of enantiomerically pure cyclopropanes from cyclopropylboronic acids

A general method for the stereocontrolled synthesis of cyclopropanes is described. Various, highly stable, enantiomerically pure alkenylboronic esters 13 have been conveniently synthesized by the direct hydroboration of alkynes 11 using the new chiral 1,3,2-dioxaborolane 15. The high stability was also demonstrated by the selective deprotection of a tert- butyldimethylsilyl protecting group without hydrolyzing the boronic ester. The diastereoselective cyclopropanation of the olefins was achieved by the palladium(II) acetate catalyzed decomposition of diazomethane. This process was optimized giving cyclopropylboronic esters 20/21 in high yield (89-99%) and with good to excellent diastereomeric ratios (up to 95:5). The diastereomers were separated by means of MPLC and their configurations determined by X-ray crystallography (compound 21c), by transformation to known cyclopropanols, and by correlation of NMR data. Treatment with LiAlH4 followed by acidic hydrolysis yielded the enantiomerically pure cyclopropylboronic acid 27 for the first time and allowed the nearly quantitative recovery of the chiral auxiliary 3. Different protocols for the Suzuki coupling reaction of compound 27 were investigated.