Construction of Enantiomerically Enriched Diazo Compounds Using Diazo Esters as Nucleophiles: Chiral Lewis Base Catalysis

Abstract

Diazo compounds are remarkably versatile metal carbene precursors which participate in metal-catalyzed rearrangements, cycloadditions, XÀH (X = C, N, O, Si, S, etc.) bond insertions, and ylide-forming reactions with concomitant expulsion of N 2 . [1] These compounds also take part in 1,3dipolar cycloaddition reactions of a wide range of dipolarophiles with retention of the CN 2 moiety. [2] Because of their unique properties and extensive applications, the interest in the chemistry of diazo compounds has been long standing. [1e, 3] However, efficient synthesis of chiral diazo compounds, especially those with delicate functionalities, is still in urgent need. [4] Enantioselective C À C bond formation employing diazo esters as nucleophilic reaction partners provides a straightforward approach to chiral diazo compounds. [5] Nevertheless, the instability of the diazo moiety to transition metals [1,6] renders them unmanageable in organometallic catalysis, and the nature of the esters makes them less reactive in organocatalysis. [7,8] Until now, the described successful examples are focused on aldol [8,9] /Mannich-type [10] reactions under the catalysis of chiral zirconium, [9a] magnesium, [8a] scandium, [9b] and zinc [9c] complexes or chiral Brønsted acids with simple electrophiles, such as carbonyl compounds and imines (Scheme 1 a,b). Exploitation of diazo esters as nucleophiles in asymmetric catalysis remains a significant challenge.Recently, chiral Lewis bases were used to catalyze asymmetric allylic alkylation, with Morita-Baylis-Hillman (MBH) adducts as electrophiles, through a S N 2'/S N 2' cascade and has emerged as a powerful strategy for the construction of multifunctional compounds. [11] To expand the number of reactions using diazo esters as nucleophiles, and also in . Keywords: diazocompounds· fluorine · heterocycles · organocatalysis synthetic methods Scheme 5. The synthesis of optically pure N Heterocycles derived from the chiral a-allylic diazo esters 4. DMAP = 4-(dimethylamino)pyridine, Ts = 4-toluenesulfonyl. Scheme 4. Gram-scale reaction for the preparation of the optically pure a-allylic diazo esters 4. Scheme 6. PMP = para-methoxyphenyl. Angewandte Chemie 6291

Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl α-diazoacetates

“…Benzyl α-diazoester 2a was generated in two steps from β-ketoester 7 (Scheme 3a). 7 Alternatively, aryl α-diazoesters 2b–2f were synthesized from bromoacetyl bromide 8 via an esterification with various phenol derivatives followed by a diazotization (Scheme 3b). 8 …”

Catalyst-Controlled Selective Functionalization of Unactivated C–H Bonds in the Presence of Electronically Activated C–H Bonds

“…119.5 4C18' C17' C2' 121.5 (2) C15_5 C14_5 C13_5 120.3 3C22' C17' C2' 119.3 (2) C14_5 C15_5 C16_5 120.3 4C22' C17' C18' 119.1 (3) C15_5 C16_5 C11_5 120.5(3) 4H9_3 0.133(4) C11_4 0.410 (11) C12_4 0.410 11H12_4 0.410 (11) C13_4 0.410 (11) H13_4 0.410 11C14_4 0.410 11H14_4 0.410 (11) C15_40.410 11H15_4 0.410 11C16_4 0.410 (11) H16_40.410 11C11_5 0.590 11C12_5 0.590 (11) H12_50.590 11C13_5 0.590 11H13_5 0.590 (11) C14_50.590 11H14_5 0.590 (11) C15_5 0.590 (11) H15_50.590 11C16_5 0.590 (11)…”

“…Single colourless block-shaped crystals of WL-C22H16BrClO2_iso1 were chosen from the sample as supplied. A suitable crystal 0.38×0.29×0.21 mm 3 was selected and mounted on a loop with paratone oil on an XtaLAB Synergy, Dualflex, HyPix diffractometer.The crystal was kept at a steady T = 105 7K during data collection.The structure was solved with the ShelXT (Sheldrick, 2015) structure solution program usingthe Intrinsic Phasing solution method and by using Olex2 as the graphical interface.The model was refined with version 2018/3 of ShelXL 7K, Z = 4, Z' = 1, (MoK ) = 2.337 mm -1 , 23622 reflections measured, 5515 unique (Rint = 0.0377) which were used in all calculations. The final wR2 was 0.1239 (all data) and R1 was 0.0487 (I > 2σ(I)).…”

Molecular Engineering of Pyrido[3,4‐b]pyrazine‐Based Donor–Acceptor–π‐Acceptor Organic Sensitizers: Effect of Auxiliary Acceptor in Cobalt‐ and Iodine‐Based Electrolytes

“…[1,2] As one of the key components of DSSCs,o rganic sensitizers based on the donor-p-acceptor (D-p-A) motif have been widely explored due to their high molar extinction coefficients, rare-metal-free structures, and, most importantly,t heir facile molecular tailoring that allows tunablep hotovoltaic performances. [3][4][5][6][7][8][9][10][11][12] Recently,a ni mproved D-p-A construction,t he so-called D-A-p-A, in which an auxiliary heteroannulateda cceptor [13] is introducedi nto the molecular framework, has been systematically developed, which has led to excellent photovoltaic performance and photostability. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] To date, several D-A-p-Abased organics ensitizers have exhibited high powerc onversion efficiencies (PCEs) of over 10 %u nder full sun illumination (AM 1.5G, 100 mW cm À2 ), such as the indoline sensitizer YA422 (10.65 %), [31] the porphyrin sensitizer GY50 (12.75 %), [32] and the record one SM315 (13.0 %).…”