Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• conjugate alkynylation and consecutive aldol addition (Scheme 49) [91]. The chiral ruthenium complex C2 (Phebox-type)-catalyzed procedure delivered β-hydroxyketone derivatives 192 having α-propargyl groups in good yields, however, only with low diastereoselectivities (up to 3:1). While the syn-diastereomers

Asymmetric synthesis of a stereopentade fragment toward latrunculins

• Benjamin Joyeux,
• Antoine Gamet,
• Nicolas Casaretto and
• Bastien Nay

Beilstein J. Org. Chem. 2023, 19, 428–433, doi:10.3762/bjoc.19.32

• a 1,5-anti induction of the aldol reaction [18][19][20] based on chiral alkoxy partner 9. Furthermore, it could be envisaged to reduce the resulting β-hydroxyketone 7 in a diastereoselective manner to obtain a 1,3-diol. This synthetic strategy could thus bring new stereochemical opportunities to

• thiazolidinone ring, possibly leading to a strong conformational distortion of Mosher's model. The question of the resulting stereoselectivity was thus left open for later resolution. To complete this study, the 1,3-anti-diastereoselective reduction of β-hydroxyketone 21 was undertaken through the Evans

• resulting from a 1,5-anti induction by the nucleophile leading to product 21, and excluding a Felkin–Anh control by the aldehyde. This reaction validates a unique disconnection among latrunculin synthetic strategies and avoids the construction of a 4-acetyl-1,3-thiazolidin-2-one. Finally, this β

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• compound 24 was rationalized by an isomerization of the double bond prior to the cyclization step. Isolated from the Ecuadorian liverwort Anastrophyllum auritum in 1994, ent-fusicoauritone (28) is a diterpene presenting a fusicoccan skeleton with a β-hydroxyketone on the A-ring and 5 stereogenic centers

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• efficiently utilized for the synthesis of highly strained tricyclo[5.2.1.01,6]decene intermediate 214 containing a cyclobutane ring (Scheme 64). Compound 213 is an important precursor for the asymmetric total synthesis of solanoeclepin A. The formation of β-hydroxyketone 213 was achieved by Hg(TFA)2-mediated

N–O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines

• Jaipal R. Nagireddy,
• Geoffrey K. Tranmer,
• Emily Carlson and
• William Tam

Beilstein J. Org. Chem. 2014, 10, 2200–2205, doi:10.3762/bjoc.10.227

• yields (66–95%) and without the need for chromatographic purification. Keywords: azabicycloalkene; β-hydroxyketone; 2-isoxazoline; oxabicycloalkene; Raney nickel; Introduction 2-Isoxazolines 1 are practical precursors to countless structural motifs found in nature. Various carbonyl compounds 2, β

• precipitated out of solution following work-up, allowing us to bypass chromatographic purification. The product so obtained was found to be β-hydroxyketone 16a (Table 2, entry 1). Once the optimal conditions were found, various symmetrical heterobicycle-fused 2-isoxazolines were opened by Raney-Ni/AlCl3

• mediation. These results are summarized in Table 2. Compared to the parent compound 10a which gave an appreciable 93% yield of the corresponding β-hydroxyketone (Table 2, entry 1), replacement of two of the arene hydrogens for bromine atoms in 10b resulted in a lower tendency toward N–O bond cleavage (Table

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• regioselective opening [60][61] leading to the β-hydroxyketone that was temporarily masked as a TES ether. Reduction of ketone 85 with NaBH4 resulted in the formation of two diastereomeric alcohols in 2:1 ratio. To our delight flash chromatography permitted smooth separation of the two compounds. nOe studies

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• analogous procedure for aldol reaction and oxidation the TMSE β-ketoester was obtained (Scheme 17). Treatment with an excess of TBAF in THF at room temperature overnight resulted in formation of the β-hydroxyketone 63. Although the yield for this transformation remained moderate, it was higher than that

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• and 69% ee. In the previous studies by Szöllösi’s group on the dipeptide III catalysed asymmetric aldol reactions between acetone and 2-ethylbutanal in the presence of an excess of acetone (68:1) under traditional stirring affords (R)-β-hydroxyketone in moderate yield and 86% ee after 24 hours [36

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

• Raymond C. F. Jones,
• Abdul K. Choudhury,
• James N. Iley,
• Mark E. Light,
• Georgia Loizou and
• Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

• four steps by the route shown in Scheme 3, involving palladium-catalysed decarboxylative ring opening of cyclic carbonates [23]. Thus the enolate of α-tetralone was added to propenal in an aldol addition (LDA, THF, −78 °C; 86%). The second step involved the reduction of the intermediate β-hydroxyketone

Acid- mediated reactions under microfluidic conditions: A new strategy for practical synthesis of biofunctional natural products

• Katsunori Tanaka and
• Koichi Fukase

Beilstein J. Org. Chem. 2009, 5, No. 40, doi:10.3762/bjoc.5.40

• evaluate the efficiency of dehydration under the microfluidic conditions, the reactivity of β-hydroxyketone 21 and alkanol 22 were also tested (Scheme 2) [29]. Gratifyingly, both substrates provided the corresponding dehydrated products 23 and 24 in almost quantitative yields under the conditions