A Convergent and Enantioselective Synthesis of (+)‐Amurensinine via Selective C—H and C—C Bond Insertion Reactions.

Abstract

Preparative Procedures S2 Spectroscopic Data and NMR Comparison S11References S17Materials and Methods. Unless stated otherwise, reactions were performed in flamedried glassware sealed with rubber septa under a nitrogen atmosphere using dry, deoxygenated solvents. Commercially obtained reagents were used as received. Solvents were dried by passage through an activated alumina column under argon. Liquids and solutions were transferred via syringe. Reaction temperatures were controlled using an IKAmag temperature modulator. Thin-layer chromatography (TLC) was conducted with E. Merck silica gel 60 F254 pre-coated plates, (0.25 mm) and visualized using a combination of UV, anisaldehyde, ceric ammonium molybdate, and potassium permanganate staining. Preparative TLC was conducted with E. Merck silica gel 60 F254 pre-coated plates, (0.25 or 0.5 mm) and visualized using UV. ICN silica gel (particle size 0.032-0.063 mm) was used for flash column chromatography.

Asymmetric Electrochemical Arylation in the Formal Synthesis of (+)-Amurensinine

“…Carbonyl reduction of 11 with L-selectride generated the corresponding key alcohol 12, which can be converted into (+)-Amurensinine accordingtoStoltz'sprocedures. 13 Furthermore,thespectroscopy and the optical rotation of the key alcohol 12 were in agreementwiththedatapreviouslyreportedintheliterature. 13…”

“…13 Furthermore,thespectroscopy and the optical rotation of the key alcohol 12 were in agreementwiththedatapreviouslyreportedintheliterature. 13…”

“…The use of copper as the Lewis acid allowed the synthesis of 3a in moderate yield, albeit with poor enantioselectivity (entry 11). Remarkably, a series of control experiments verified the necessity of each reaction component (entries [12][13][14][15]. In the absence of Lewis acid or diamine ligand, no product was formed (entries 12-14).…”

“…11,12 In this context, we sought to develop a complementary strategy that would allow the enantioselective catalytic construction of α,α-diaryl tertiary carbonyl architecture and provide direct access to the key functional and architectural elements found in (+)-Amurensinine. [13][14][15] Electrochemical synthesis has emerged as an enabling platform for mild and efficient bond-forming reactions without the requirement of stoichiometric quantities of chemical oxidants or reductants. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] The feasibility of electrochemical synthetic strategy has been demonstrated for providing rapid access to multiple natural product scaffolds selectively.…”

Modern Organic Synthesis with α-Diazocarbonyl Compounds

“…348−350 For example, Stoltz and co-workers reported selective aromatic substitution reaction as a key step in the total synthesis of (+)-amurensinine (115) (Scheme 138). 350 As with other diazocarbonyl reaction types, three-component reactions initiated by aromatic functionalization have also begun to emerge. Hu and co-workers reported the first asymmetric functionalization of aromatic C−H bonds through a three-component reaction of N,N-disubstituted anilines with α-diazoesters and imines in the presence of Rh(II)/chiral phosphoric acid cocatalysts.…”