Stereochemical consequences in the deprotonation of enoates

Galatsis, Paul; Manwell, Jeffrey J.; Millan, Scott D.

doi:10.1016/0040-4039(96)01144-6

Cited by 21 publications

(6 citation statements)

References 19 publications

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“…We were also pleased to find that ( Z )-β,γ-unsaturated esters 6i,j led with complete stereocontrol (within the limits of detection of 1 H NMR and capillary GC) to the desired ( Z )-vinyldiazoesters 7i,j in excellent overall yield and that no isomerization or migration of the double bond occurred in our conditions 10b. This represents the first and indeed a general route to this kind of diazo precursor.…”

Section: Discussionsupporting

confidence: 51%

A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

et al. 1997

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R-amino, and R-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral R-vinyldiazoesters and Doyle's chiral catalyst Rh 2 (MEPY) 4 . In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh 2 (MEPY) 4 -catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports. DiscussionSynthesis of (E)-and (Z)-Vinyldiazoesters. Vinyldiazomethanes have been used in various contexts in the

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Section: Discussionsupporting

confidence: 51%

A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

et al. 1997

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“…A deconjugating isomerization of compound 4 was expected to give the corresponding 4‐propenylpyroglutamate, which might be transformed to the appropriate 4‐propenylproline. At least for simple models studied before, this transformation often proceeded in such a way that the ( E )‐α,β‐unsaturated esters or amides gave the ( Z )‐deconjugated products, and in contrast a ( Z )‐configured conjugated double bond was converted into an ( E )‐configured double bond with good selectivity 5. The N ‐Boc‐protected tert ‐butyl ( S )‐4‐( E )‐propylidenepyroglutamate 4 6 was prepared as described by Ezquerra et al7 for the corresponding ethyl ester.…”

Section: Resultsmentioning

confidence: 99%

Convergent Syntheses of N‐Boc‐Protected (2S,4R)‐4‐(Z)‐Propenylproline and 5‐Chloro‐1‐(methoxymethoxy)pyrrol‐2‐carboxylic Acid − Two Essential Building Blocks for the Signal Metabolite Hormaomycin

et al. 2004

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An efficient and scalable synthesis of enantiomerically pure N-Boc-protected 4-(Z)-propenylproline (15) using the conventional Wittig reaction to construct the double bond has been developed [11% yield over 8 steps from N-Boc-pro- (29)] was prepared along a reasonably efficient synthetic route applying the thermal rearrangement of 2-azido-6-chloropyridine N-oxide (22) as a key step in fairly good overall yield [9% over 7 steps from easily accessible 2,6-dichloro-

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“…If this is so, then cyclization of pure 19 should give rise to 20 with excellent enantiocontrol. The origin of this loss of olefin geometry is currently under scrutiny, and preliminary results have been published …”

Section: Resultsmentioning

confidence: 99%

Enantioselective Construction of Cyclic Ethers by An Aldol-Cyclization Sequence

1997

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We have modified the substrate used in deconjugative aldol-cyclizations by incorporating the Evans chiral auxiliary. The deconjugative aldol step, using boron enolates, gave the expected products with complete syn-aldol stereochemistry. These compounds could then undergo an iodine-mediated cyclization to form optically active products. Oxetanes and fused ring tetrahydrofurans were easily assembled with a variety of substitution patterns and with excellent enantiocontrol. The deconjugation of acyclic chiral enimides resulted in the loss of control of olefin geometry. However, these compounds did appear to cyclize with excellent enantiocontrol.

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Stereochemical consequences in the deprotonation of enoates

Cited by 21 publications

References 19 publications

A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

Convergent Syntheses of N‐Boc‐Protected (2S,4R)‐4‐(Z)‐Propenylproline and 5‐Chloro‐1‐(methoxymethoxy)pyrrol‐2‐carboxylic Acid − Two Essential Building Blocks for the Signal Metabolite Hormaomycin

Enantioselective Construction of Cyclic Ethers by An Aldol-Cyclization Sequence

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