Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• with diverse biological activities [17]. The key step first involved the rhodium carbenoid-mediated OH insertion/Claisen rearrangement following complexation of diazoester 56 and allylic alcohol 57 to produce intermediate 58 (Figure 13). Addition of BF3·OEt2 to the reaction mixture then catalyzed the α

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• trifluoromethyl-substituted cyclopropylcarbinyl systems were prepared by addition of the carbene derived from the diazoester 56 to vinyltrimethylsilane as shown in Scheme 12. Reduction of the ester mixture 57 with lithium aluminum hydride gave a chromatographically separable mixture of alcohols 58 and 59

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• –Stevens-derived diazoesters 23 and 27, respectively. Only triethylsilyl-protected diazoester 27 proved viable to deliver a diazoketone 28. The latter underwent stereoselective carbonyl ylide formation–cycloaddition with methyl glyoxylate and acid-catalysed rearrangement of the resulting cycloadduct 29, to

• ,S-configuration found in several monoalkylated tartaric acid motif-containing natural products. Keywords: alkylation; cycloaddition; diazoester; epimerisation; tartaric acid; Introduction Since their isolation was reported in the early 1990s [1][2], the squalestatins/zaragozic acids (e.g

• Discussion The general viability of the α-ketoester to α-diazoester functional group interconversion envisaged in Scheme 2 (10 → 3) was readily established on a simpler but closely structurally-related system (Scheme 3). Thus, the known Z-hydrazone 12, previously prepared by us from α-ketoester 11 in 75

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• crucial for the intramolecular cyclopropanation reaction in a water/ether biphasic medium. The water-soluble catalyst could be reused at least six times with little loss in yield and enantioselectivity. Keywords: asymmetric synthesis; carbene transfer; cyclopropanation; diazoester; intramolecular

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• temperature or on heating with dirhodium tetraacetate or the even more active dirhodium tetraoctanoate, did not lead to a notable decomposition of diazoesters 2a,b. At the same time it was found that at elevated temperatures, for example on refluxing the diazoester 2a with thioacetamide 1a in the presence of

• , entry 6). Thus the experiments with diazomalonate 2a and thioacetamide 1a demonstrated that the most appropriate conditions for the catalytic reaction of a diazo carbonyl compound with thioamides, were the employment of an 1.2-fold excess of diazoester 2, Rh2(OAc)4 or Rh2(OPiv)4 as the catalysts, and

• been used as the catalysts, but with none of them a detectable conversion of the reagents was achieved. By and large this observation correlates with the literature data regarding relative inertness of the cyclic diazoester 2c in Rh(II)-catalyzed reactions in comparison with diazomalonates and the

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• ) at the ortho position was methyl, or via coupling reactions with C4 units when X was a bromo substituent. The cis-fused tricyclic core of 3 was assumed to be constructed by a stereoselective C–H insertion of diazoester 4, which can be readily prepared from the Weinreb amides 5 or 6 via Claisen

• -dimethylimidazolinium hexafluorophosphate (ADMP) [40][41][42] to give the diazoester 14. Rhodium catalysed C–H insertion [43][44] of 14 proceeded smoothly to furnish the tricyclic ketoester, which was found to be unstable to purification on column chromatography, presumably due to decomposition of the ketoester moiety

• than that of adduct 6 (93% ee) (Scheme 4). Fortunately the diazoester 20, as similarly derived as in Scheme 3, was obtained as a crystalline solid, and one recrystallization increased the ee to 95%. The tricyclic scaffold 21 with all four stereocenters of the desired configuration was synthesized in 67

A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones

• Jubi John,
• Eliza Târcoveanu,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 1462–1470, doi:10.3762/bjoc.10.150

• synthesis of 3(2H)-furanones from activated alkenes [40]. Pd-catalyzed synthesis of 3(2H)-furanone from tosylimine 1a. Mechanism of formation of the 3(2H)-furanone derivative from an imine. Pd-catalyzed synthesis of 3(2H)-furanone from diazoester 19a. Synthesis of aza-prostaglandin analogue. Optimisation

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• 82. Diazotransfer using p-ABSA [86] yielded diazoester 83. Selective rhodium-catalyzed cyclopropanation of the cis-double bond [87][88] of diene 84 [89] furnished cis-divinylcyclopropane 85, which underwent DVCPR upon Kugelrohr distillation at 140 °C to give bicyclic 86. Selective hydrogenation of

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• analogously; it should be noted that different approaches were taken to obtain the methyl ester analogue of 11b and other similar sulfur-containing α-diazo-β-ketoesters [14][15][16]. We found that diazoester 8a can also be prepared by acylation of ethyl diazoacetate (two equivalents, one equivalent serving to

• , and therefore, diazoesters 8a–c were also obtained in (almost) racemic form. As a consequence, diazoester 8a was prepared subsequently from DL-methionine. On the other hand, the preparation of N-phthaloylated diazoester 8a via the aminoacid chloride route (Scheme 3) seems to occur with only a little

• -catalysed ylide-forming reactions A sample of racemic diazoester 8a, prepared from DL-methionine, was exposed to a catalytic amount of dirhodium tetraacetate in boiling benzene. Two products were isolated and identified, the six-membered cyclic sulfonium ylide 12a (13% yield) and the carbonyl ylide dimer

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• tributyltin fluoride [112]. After protecting group manipulations and formation of the diazoester 138 with p-nitrobenzenesulfonylazide (PNBSA), the key carbene insertion was achieved using copper(I) in the presence of bis-oxazoline 139. A 9:1 ratio of 141 and 142 was obtained after direct chloranil oxidation

• circumventing this regioselectivity issue by exploiting the enantioselective intramolecular C–H insertion of diazoester 144 into a meso pyrrolidine using chiral catalyst 145. Unfortunately the reaction displayed low enantio- and diastereoselectivity, with the major isomer 146 having an ee of only 51% (Scheme 40