Premium
Substrate‐Controlled Michael Additions of Titanium Enolates from Chiral α‐Benzyloxy Ketones to Conjugated Nitroalkenes
Author(s) -
GómezPalomino Alejandro,
Barrio Adrián,
GarcíaLorente Pedro,
Romea Pedro,
Urpí Fèlix,
FontBardia Mercè
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201701055
Subject(s) - chemistry , nitroalkene , lewis acids and bases , electrophile , michael reaction , nitrile , diastereomer , organic chemistry , aryl , reactivity (psychology) , enantioselective synthesis , ketone , conjugated system , substrate (aquarium) , regioselectivity , medicinal chemistry , alkyl , catalysis , medicine , alternative medicine , polymer , oceanography , pathology , geology
Lewis acid mediated substrate‐controlled reactions of the titanium(IV) enolates of chiral α‐benzyloxy ketones with conjugated nitroalkenes give 2,4‐ anti ‐4,5‐ syn Michael adducts in good yields and diastereomeric ratios. The supplementary Lewis acid plays a key role in the outcome of these transformations, probably as a consequence of the formation of dimetallic enolates that increase the reactivity of the enolate and direct the approach of the nitroalkene. Importantly, the most appropriate Lewis acid depends on the electrophilic partner: TiCl 4 is the most suitable Lewis acid for β‐aryl‐nitroalkenes, whereas the best results for β‐alkyl‐nitroalkenes are obtained with SnCl 4 . Finally, the nitro group of the resultant compounds can be converted into the corresponding amine, oxime, and nitrile groups under mild conditions, which permits the synthesis of a variety of enantiomerically pure derivatives in excellent yields.