Highly Enantiomerically Enriched Ketone Homoenolate Reagents Prepared by (−)‐Sparteine‐Mediated γ‐Deprotonation of Achiral 1‐Alkenyl Carbamates

Mild and Site-Selective Allylation of Enol Carbamates with Allylic Carbonates under Rhodium Catalysis

“…To demonstrate the synthetic utility of allylated enol carbamates, the deprotection of 3a and 4a using TMSOTf was performed (Scheme ). Unexpectedly, allylic alcohol 3a was converted into 2,4-dienone 5a and branched allylic alcohol 5b . Additionally, in contrast to deprotection of allylic alcohol 3a , terminal allylated compound 4a under the identical reaction conditions provided the corresponding ketone 5c and unexpected hydrated compound 5d .…”

Novel Approach to the (–)‐Sparteine‐Mediated Synthesis of Kainoids:Total Synthesis of (–)‐α‐Kainic Acid by (–)‐Sparteine‐Mediated Deprotonation

“…The usual oxidative methods26 are not applicable to vinyl carbamates 37a and 37b due to the reactive additional trisubstituted double bond. Moreover, attempts to convert the vinyl carbamate 37a into aldehyde 38a by using methyllithium27 or TMSOTf28 failed. In light of these results, we used an indirect oxidation method consisting in a vinylic deprotonation by applying tert ‐BuLi followed by quench with MeSSMe 29.…”

Sequential Double α-Arylation of N-Allylureas by Asymmetric Deprotonation and N→C Aryl Migration

“…We found that better er’s and yields of rearranged products 7 were obtained when lithiation/rearrangement conditions similar to those in Scheme were used, but with LDA replaced by a chiral lithium amide . Both enantiomers of a range of suitable chiral amines 12·H and 13·H or their readily handled hydrochloride salts are available commercially or in a few steps from inexpensive starting materials.…”

“…Racemic product was also formed slowly from E - 6b (Table ): rapid formation of a low (<25%) yield of enantiomerically enriched 7b was observed from a 4:1 mixture of E - and Z- 6b , followed by a slower increase in yield and erosion of product er . Enantioselective formation of an organolithium by a chiral lithium amide other than by asymmetric deprotonation of one of a pair of enantiotopic protons is apparently unprecedented …”