116179-01-2Relevant academic research and scientific papers
General allylic C-H alkylation with tertiary nucleophiles
Howell, Jennifer M.,Liu, Wei,Young, Andrew J.,White, M. Christina
supporting information, p. 5750 - 5754 (2014/05/06)
A general method for intermolecular allylic C-H alkylation of terminal olefins with tertiary nucleophiles has been accomplished employing palladium(II)/bis(sulfoxide) catalysis. Allylic C-H alkylation furnishes products in good yields (avg. 64%) with excellent regio- and stereoselectivity (>20:1 linear:branched, >20:1 E:Z). For the first time, the olefin scope encompasses unactivated aliphatic olefins as well as activated aromatic/heteroaromatic olefins and 1,4-dienes. The ease of appending allyl moieties onto complex scaffolds is leveraged to enable this mild and selective allylic C-H alkylation to rapidly diversify phenolic natural products. The tertiary nucleophile scope is broad and includes latent functionality for further elaboration (e.g., aliphatic alcohols, α,β-unsaturated esters). The opportunities to effect synthetic streamlining with such general C-H reactivity are illustrated in an allylic C-H alkylation/Diels-Alder reaction cascade: a reactive diene is generated via intermolecular allylic C-H alkylation and approximated to a dienophile contained within the tertiary nucleophile to furnish a common tricyclic core found in the class I galbulimima alkaloids.
REGIOCHEMICAL DIVERSITY IN ALLYLIC ALKYLATIONS VIA MOLYBDENUM CATALYSTS
Trost, Barry M.,Lautens, Mark
, p. 4817 - 4840 (2007/10/02)
The use of molybdenum as a template to control regioselectivity in allylic alkylations is explored.The feasibility of performing allylic alkylations with preformed ?-allylmolybdenum comlplexes is established.As in palladium reactions, addition of excess phosphine has a profound effect on the rate these reactions.A catalytic reaction based upon molybdenum hexacarbonyl is developed.Using malonate anion, excellent regioselectivity for attack at the more substituted end of an allyl system regardless of the positional identity of the initial leaving group exists.With β-ketoesters, substrates which possess a secondary and a primary carbon in the allyl unit lead to preferential attack at the secondary carbon.However, substrates that possess a tertiary and a primary carbon at the termini lead to attack at the primary carbon.Anions derived from substituted malonates and 1,3-diketones lead to substitution at the less substituted position of allyl systems.The presence of strongly electron withdrawing substituents has little effect on these orientational blases.Mechanistic implications of these results are discussed.
