Synthesis of sulfur karrikin bioisosteres as potential neuroprotectives

• Martin Pošta,
• Václav Zima,
• Lenka Poštová Slavětínská,
• Marika Matoušová and
• Petr Beier

Beilstein J. Org. Chem. 2022, 18, 549–554, doi:10.3762/bjoc.18.57

• was treated with triethylamine in order to obtain the eliminated product exclusively. The second elimination over C4–C5 resulted in a low yield of 26 (41%) (not shown in Scheme 5) and a high (Ph3P)4Pd catalyst load (10%) was necessary, despite the fact that allylic carbonates are good substrates in

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• formations of enantioenriched α-substituted allylic boronates take place in high yields and site-selectivity (>98% SN2′) starting with either trans- or cis-disubstituted alkenes 313, as well as linear or branched alkyl and aryl trisubstituted allylic carbonates 314. The further oxidation of the boronated

• carbonates to deliver the targeted products (Scheme 51) [94]. In addition to allylic carbonates, allylic acetals (319) were also used for C–B bond formation that, in the presence of CuCl/(R,R)-BenzP* and stoichiometric amounts of KO-t-Bu, provide access to α-chiral linear or carbocyclic (γ-alkoxyallylic

• products (e.g., 316) yielded nonracemic secondary (e.g., 317) and tertiary alcohols (e.g., 319). The presence of Cu(OTf)2, an imidazolium salt, and NaOMe leads to a chiral NHC–Cu complex, which, in the presence of B2pin2, generates the corresponding B–Cu species followed by its addition to allylic

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• . The synergistic palladium/copper-catalyzed reaction of aromatic aldehydes, allylic carbonates, and a silylboronate produces the corresponding homoallylic alcohol derivatives. This process involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species and the subsequent palladium

• electrophile [8][10][11]. This paper describes in full detail the racemic system using allylic carbonates. The allylic cross-coupling of aromatic aldehydes and allylic carbonates with a silylboronate by the merging of a copper–N-heterocyclic carbene catalyst and a palladium–bisphosphine catalyst produced

• and allylic carbonates 2. Methyl, tert-butyl and fluoro substituents were tolerated at the ortho- or para-positions of the aromatic aldehyde (3ba–da). 2,6-Dimethylphenyl- or 1-naphthyl moieties as the γ-substituent of the primary allylic carbonate were tolerated in the reaction (3ab and 3ac). Cinnamyl

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• -linear ratios and enantioselectivities. In 2013, Gouverneur and co-workers [94] demonstrated the regio and stereocontrolled fluorination of allylic carbonates with [Ir(COD)Cl]2 as the catalyst and TBAF(t-BuOH)4 as the fluoride source to produce branched and linear allylic fluorides (Scheme 46

Highly selective palladium–benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions

• Antonio Monopoli,
• Pietro Cotugno,
• Carlo G. Zambonin,
• Francesco Ciminale and
• Angelo Nacci

Beilstein J. Org. Chem. 2015, 11, 994–999, doi:10.3762/bjoc.11.111

• from Pd2dba3 and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed. Keywords: active methylene compounds; allylic carbonates; Pd–benzothiazol-2-ylidene complex; Tsuji–Trost

• , as a precatalyst in the Tsuji–Trost allylation of active methylene compounds using carbonates as allylating agents (Scheme 1). Results and Discussion Allylic carbonates are suitable reagents for the Tsuji–Trost allylation as they enable to work under neutral conditions. The base required for

• by extending the coupling to a series of 1,3-dicarbonyl compounds and allylic carbonates (Table 2). For these reactions, to further simplify the operating procedure of the proposed protocol, we chose to use the palladium–carbene catalyst prepared in situ as reported above (Table 1, entries 20–22

Relay cross metathesis reactions of vinylphosphonates

• Raj K. Malla,
• Jeremy N. Ridenour and
• Christopher D. Spilling

Beilstein J. Org. Chem. 2014, 10, 1933–1941, doi:10.3762/bjoc.10.201

• phosphorus; relay; vinyl phosphonate; Introduction Over the last two decades, we have developed reactions for the formation of chiral non-racemic γ-substituted vinylphosphonates [1][2][3][4][5][6][7][8][9]. In particular, carbonate derivatives 1 (phosphono allylic carbonates) of allylic hydroxy phosphonates

• complete chirality transfer. Various carbon, nitrogen, and oxygen nucleophiles participate in the palladium-catalyzed substitution reactions of phosphono allylic carbonates 1. Vinylphosphonates formed in this way, for example 2a–e (Figure 1), have been used in the synthesis of the natural products

• relay step in the cross metathesis reaction mechanism. Natural products prepared using vinyl phosphonate intermediates. Palladium catalysed reaction of phosphono allylic carbonates. Approaches to the synthesis of centrolobine. Relay ring closing metathesis and relay cross metathesis. Cross metathesis

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• . Results and Discussion On installation of pyrimidine bases into the gem-difluorinated allylic carbonates 1 and 4, our group found that the γ-substitution products 2, 3 and 5 were surprisingly generated exclusively in good yields, respectively, when the compounds 1 and 4 reacted with suitably protected

• -catalyzed reactions of cyclic gem-difluorinated allylic carbonates 1 and 4 proceeded via the symmetric Pd-π-allyl bonding and highly regioselective γ-substitution resulted from the neighboring gem-difluoromethylene group. We propose that the present work opens a new avenue for the further insight into the

• Pd-catalyzed allylic substitution reactions. X-ray structure of trans-trans dimer 8. Pd-catalyzed allylic substitution of the gem-difluorinated allylic carbonates 1 and 4. Synthesis of trans-trans dimer 8 and syn-syn dimer 9. Reaction of trans-trans dimer 8 with 3-benzoylthymine sodium / PPh3