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Please login to access the full content or check if you have access via Variation 2: Heteroatom-Substituted Allyl Anions

DOI: 10.1055/sos-SD-025-00247

Göttlich, R.Science of Synthesis, (200725389.

The reaction with electrophiles of heteroatom-substituted allyl anions gives enol derivatives or enamines that can be hydrolyzed to form the corresponding aldehydes. The main problem is that the attack of an electrophile on an allyl anion can occur at either the α- or the γ-position, the latter leading to undesired products (Scheme 33). The first anions of this kind that were used as homoenolates were deprotonated allyl ethers[‌137‌] and allyl thioethers,[‌138‌] which give mixtures of the two possible regioisomers on reaction with electrophiles. Thioenol ethers, as well as the corresponding sulfoximines,[‌139‌‌141‌] are often difficult to transform into aldehydes, and are therefore not discussed here. The use of sterically hindered silyl ethers leads to better γ-selectivities in the alkylation reaction,[‌142‌] but the reaction with carbonyl compounds shows the opposite selectivity.[‌137‌,‌143‌]

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