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Results tagged with stereoselectivity
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user 16683
For questions about reactions that favour the formation of one or more stereoisomers.
8
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Why are lithium (Z)-enolates more stereoselective than (E)-enolates in aldol reactions?
In aldol reactions, it is apparently a general rule of thumb that (Z)-enolates give higher stereoselectivity (for the syn aldol product) than (E)-enolates do for the anti product. …
- 71.9k
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Why do stabilised ylids lead to trans alkenes in the Wittig reaction?
Why do stabilised ylids (such as $\ce{Ph3P=CHCO2Me}$) lead to (E)-alkenes in the Wittig reaction, in contrast to unstabilised ylids which are (Z)-selective?
The (E)-alkene is formed from stereospecif …
- 71.9k
6
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1
answer
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Chelation-controlled aldol: why is the α substituent pseudo-axial?
In this Mukaiyama aldol reaction, taken from a 1999 paper by D.A. Evans,1 when $\ce{TiCl4}$ was used as the Lewis acid catalyst, the aldehyde 4a formed a chelated intermediate whereas 4b did not (due …
- 71.9k
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Stereoelectronic effects in torquoselectivity of 4π electrocyclic opening
Thermal 4π electrocyclic ring openings of cyclobutenes to form butadienes are known to proceed in a conrotatory manner, consistent with the Woodward–Hoffmann rules. However, there are two different co …
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Why do Grignard reagents add to propargyl alcohols?
On top of that, what is the rationale for the selectivity observed (both regio- and stereoselectivity)? …
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