Rhodium‐Catalyzed Asymmetric Allenylation of Sulfonylimines and Application to the Stereospecific Allylic Allenylation

Abstract

Ther hodium-catalyzeda symmetric allenylation of sulfonylimines is disclosedp roviding silyl homoallenylamide productsi nu pt o9 9:1 er. Through subsequent activation of the C À Nb ondo f the silyl homoallenyl sulfonamide,p alladium-catalyzed stereospecific allylic allenylation could be achieved giving C À Cb ond formation with high chirality transfer.T he synthetic utility of both the silyl homoallenyl sulfonamides andt he silyl homoallenyl malonatesasb is(nucleophiles) is demonstrated.

Computationally Assisted Mechanistic Investigation and Development of Pd-Catalyzed Asymmetric Suzuki–Miyaura and Negishi Cross-Coupling Reactions for Tetra-ortho-Substituted Biaryl Synthesis

“…In an effort to further reduce the loading of the boron coupling partner, we next examined other boron derivatives in the coupling reaction in an effort to reduce protodeboronation side-reactions (Scheme 6). Use of the glycol ester ( 16b ) that was optimal in Cammidge’s system 13d and has been recently shown to give improved transmetalation rates in Suzuki-Miyaura cross-coupling reactions 30 gave similar enantioselectivities as that observed with boronic acid 16a but did not afford full conversion in the reaction, even at prolonged reaction times. Use of the pinacol ester 16c allowed for reduction of the boron coupling partner to 2 equiv; however, long reaction times were required and a slight loss in enantiopurity was obtained.…”

P-Chiral Monophosphorus Ligands for Asymmetric Copper-Catalyzed Allylic Alkylation

“…Transition metal catalyzed allylic substitution with carbon nucleophiles is a powerful carbon–carbon bond-forming reaction . A number of enantioselective transformations have been realized with various transition metal catalysts including Pd, Mo, W, Ru, Rh, and Ir by employing stabilized carbon nucleophiles such as malonates. For enantioselective allylic alkylation with nonstabilized carbon nucleophiles, Cu catalyst is most frequently employed, allowing the enantioselective installation of simple alkyl groups at the allylic position …”

Allenylation and Propargylation Reactions of Ketones, Aldehydes, Imines, and Iminium Ions Using Organoboronates and Related Derivatives

“…Sieber and co-workers 45 reported that the rhodiumcatalyzed enantioselective allenylation reactions of N-tosylimines 74 with the pinacol propargylboronate 5 provided the N-tosyl-α-allenylamines 95 in generally good yields and with good to excellent enantioselectivities (78-98% ee) (Scheme 51). 4-Chlorobenzaldehyde imine only gave a 35% yield (92% ee).…”

“…The enyne 130, prepared from the α-allenyl amine 128 underwent a ruthenium-catalyzed cycloisomerization reaction to give the hexahydrocyclohepta[c]pyrrole 131 in 85% yield (Scheme 58). 45…”