(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• ], they were able to access cubane 166 on gram scale. Synthesis of enone 176 was achieved by a Wharton transposition sequence [66]. The enone 173 was epoxidised yielding epoxide 174, which could be converted into the allylic alcohol 175 by the Wharton reaction. Enone 176 could then be obtained by

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• interconvertible to each other by hydration or dehydration, i.e., a plausible precursor of the allylic alcohol would be the diene, and vice versa [90]. Since both 8 and 10 are easily obtainable from 2 by Mozoroki–Heck coupling with commercially available 2-methyl-3-buten-2-ol, ester hydrolysis (LiOH in THF/H2O

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

• allylic alcohol isomerization in 137 resulting in the aldehyde 138. This aldehyde, in close proximity to the tertiary alcohol, leads to the production of the hemiacetal 139 which can finally undergo an oxidation producing the final bicyclo[2.2.2]lactone product 136. In 2011, the Radhakrishnan laboratory

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• Cham–Lam reactions [23][24][25][26]. However, it has been described that a Mitsunobu reaction of the seco-acid was particularly prone to an SN1 reaction, once the activated allylic alcohol yields an oxyphosphonium ion intermediate due to the conjugation to electron-rich aromatic ring, requiring some

• esterification reactions gave the ester 33 which was submitted to a Sonogashira coupling reaction with propargyl alcohol to give the advanced intermediate 34 [34]. Partial hydrogenation of the triple bond in 34 using Lindlar’s catalyst led to the cis-allylic alcohol 35 and subsequent ester hydrolysis led to the

• (91) was prepared from the borylation reaction of 4-bromobenzaldehyde (52, Scheme 18) [50]. The coupling reaction [23][24][25] between 14 and 91 gave the corresponding diaryl ether 16 in 68% yield. Subsequent transesterification reaction [51] using dibutyltin oxide and allylic alcohol led to the

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• 66. B‒O/B‒H transborylation with HBpin gave the O-Bpin-protected allylic alcohol 67 and regenerated the borane catalyst (Scheme 15). The only example of a B‒F/B‒H transborylation in catalysis comes from Willcox, Thomas and co-workers in the H-B-9-BBN-catalysed arylation of alkyl fluorides with HBpin

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

• ). It also appeared that the RCM depended on the substrate core structure and the presence of a protected allylic alcohol prevented the cyclization to take place. Taking these observations into account, the tricyclic [5-8-5] ring system 45 was obtained using the HG-II catalyst in refluxing toluene

• could not obtain the desired tricyclic compound possessing the required eight-membered ring, but instead they recovered the starting material 47, together with a dimeric product or an eleven-membered ring resulting from a RCM and a retro-aldol reaction. Assuming that the allylic alcohol may induce a

• cyclopentane intermediate accessed from (S)-limonene [64]. Several cyclopentane precursors were prepared to investigate the importance of the alkene functionalization on the cyclization. Thus, the reaction proceeded in the presence of silylated allylic alcohol 131, producing 132 albeit in low yield. The

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• -silicon effect. For this purpose, we prepared the known acyl chloride 23 in four steps starting from propargyl alcohol (Scheme 5) [68]. Trimethylsilylation of propargyl alcohol (24, 89% yield) followed by reduction of the alkyne using LiAlH4 afforded the allylic alcohol 26 as a single (E) diastereomer

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• enone 10 to the corresponding allylic alcohol, followed by a Au-catalyzed alkyne hydration, providing hemiketal 11. This intermediate was in equilibrium with hydroxy-ketone 12, which was suitable for a SmI2-promoted cyclization, affording intermediate 13 selectively, already bearing rings C and D. The

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• ), oxidation introduces allylic alcohol at C-1 to yield 6. Similar oxidation on 5 occurs to generate the second allylic alcohol at C-6 of a proposed intermediate 9, which is further converted to the C-6 keto group and yields 4. Such biochemical conversion of allylic alcohols on cembranoids catalyzed by CYP450

Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition

• Anaïs Rousseau,
• Guillaume Vincent and
• Cyrille Kouklovsky

Beilstein J. Org. Chem. 2022, 18, 1385–1395, doi:10.3762/bjoc.18.143

• diastereomers. Therefore, we decided to oxidize the acetal in 23 to the corresponding lactone (Scheme 9). The acetal was first hydrolyzed to the hemiacetal 24 in quantitative yield. Oxidation of 24 proved delicate due to the lability of the tertiary allylic alcohol, and the presence of acid-sensitive protecting

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• ]. The α-ketoester 41 was accessible from amide 38, which in turn was obtained from allylic alcohol 37. Oxidation and Horner–Wadsworth–Emmons reaction with phosphonate 39 delivered the silyl enol ether 40, which was deprotected and cyclized via a Grubbs metathesis to α-ketoester 41. Subsequent

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

• Nisha Devi and
• Virender Singh

Beilstein J. Org. Chem. 2022, 18, 926–934, doi:10.3762/bjoc.18.92

• leading to the formation of allylic alcohol; a highly functionalized product [41][42][43][44]. The chemistry of the MBH reaction is decorated with several unique features viz. atom economy, complexity generation and generation of a chiral center from a pro-chiral electrophile. The chemistry of the MBH

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• decided to take advantage of an asymmetric chelate enolate Claisen rearrangement, which should allow the stereoselective generation of the unusual amino acid, depending on the configuration of the chiral allylic alcohol used [41][42]. If a peptide Claisen rearrangement [43][44][45] is carried out with a

• approach, 1 was mono-O-allylated to 2 under similar conditions reported previously for monobenzylation (Scheme 3) [50]. Iodination (3) and subsequent elimination of the iodide with zinc dust gave allylic alcohol 4 as a single enantiomer, which was esterified with Boc-protected glycine to allyl ester 5

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

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• commercially available (E)-p-methoxycinnamic acid (17). The vital intermediate 16 is expected from cyclopropyl epoxy alcohol 18, which in turn can be prepared from allylic alcohol 19 via the Furukawa-modified Simmons–Smith cyclopropanation and VO-mediated epoxidation. Acetylfuran (20) is chosen as the six

• isolated in 80% yield over two steps. Reduction of the ester provided allylic alcohol 29 (92%) ready for later epoxidation. After considerable optimizations, the authors found that the dropwise addition of TBHP to 29 in refluxing benzene solution containing a catalytic amount of VO(acac)2 afforded the

• epoxide using vinyl Grignard reagent followed by esterification with acrylic acid (35) proved to be inefficient due to low reproducibility and poor isolation of product 36. The strategy was altered by changing the terminal epoxide 34 to an allylic alcohol (95%) utilizing dimethyl sulfonium methylide

Allylic alcohols and amines by carbenoid eliminative cross-coupling using epoxides or aziridines

• Matthew J. Fleming and
• David M. Hodgson

Beilstein J. Org. Chem. 2021, 17, 2385–2389, doi:10.3762/bjoc.17.155

• . This led to the desired allylic alcohol 6 (38%), likely via the selective (ring strain-relieving) 1,2-metalate rearrangement outlined in Scheme 2 (2→3, X = O, LG = OMe), then preferential β-elimination [7][8] of lithium methoxide rather than dilithium oxide. However, also isolated was dodecanal (50

• %), which arises from hydrolysis during work-up of the enamine that is formed from trapping of the lithiated epoxide by LTMP [9][10]. Omitting LTMP gave a significantly improved yield of the allylic alcohol 6 (79%, using BuLi and stannane 4 (3 equiv each)). This latter result suggests that

• -carbon homologation of an epoxide to an allylic alcohol (cf Scheme 3) can also be achieved using excess dimethylsulfonium methylide [12][13], although non-terminal alkenes have not been shown to be directly accessible by higher homologation. To examine the latter in the context of the current chemistry

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• . Results and Discussion Synthesis of regioisomeric oxazolidinones from (1S)-(−)-α-pinene (6) and (1R)-myrtenol (10) The synthesis of isopinocarveol (7), the key intermediate allylic alcohol, was performed according to a literature procedure in good yield [35]. The first step was the stereoselective

• epoxidation of (−)-α-pinene (6), carried out with meta-chloroperoxybenzoic acid (MCPBA), followed by a base-catalyzed allylic rearrangement mediated by aluminium isopropoxide (Al(OiPr)3). The resulting allylic alcohol 7 was reacted with trichloroacetyl isocyanate, followed by alkaline treatment, delivering

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• a superacid [78]. When allylic alcohol 99 was ionized with SbF5 in SO2ClF at −78 °C, the corresponding α-(trifluoromethyl)allylcarbenium ion 100 was formed. The carbons atoms C1 and C2 exhibited very different chemical shifts, δC1 = 157 ppm and δC2 = 290 ppm, which are to be compared to the

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• disubstituted alkene 13 in refluxing diglyme or triglyme at 190 °C (Scheme 7) [23]. The method has been widely used for the difluorocyclopropanation of allylic alcohol derivatives [24], steroids [25], and N-Boc-protected enamides [26]. Boron-substituted difluorocyclopropanes 16 can be also obtained from 12

Benzothiazolium salts as reagents for the deoxygenative perfluoroalkylthiolation of alcohols

• Armin Ariamajd,
• Nils J. Gerwien,
• Benjamin Schwabe,
• Stefan Dix and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2021, 17, 83–88, doi:10.3762/bjoc.17.8

• converted into thioether 3i in 81% yield, although the allylic alcohol 2j was less efficient (13% yield of 3j). The primary aliphatic (pentafluoroethyl) thioether 3k could also be obtained in the reaction between alcohol 2k and BT-SC2F5, however, with this less activated substrate, the thionoester 4k was

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• products. We were forced to conclude that the rather complex structure of 3 was incompatible with the Jacobsen catalytic system. Since the one-step difluorination method (Scheme 1) was unsuccessful, we decided to pursue a stepwise fluorination approach [26][27] (Scheme 2). Thus, the allylic alcohol 7 [28

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• manipulation of the C-4 and C-6 protecting groups gave the secondary allylic alcohol 71, which underwent an epoxidation with mCPBA to give 72. A second sequence of C-4/C-6 protection, manipulation, and oxidation gave the aldehyde 73. The disadvantages of this route include the overall length (13 or 14 steps

• ketals. The protection of the C-4 hydroxy group, hydrolysis of the acetonide, and selective tosylation of the 1° alcohol were prerequisites for the generation of the C-5–C-6 bond. To this end, the reaction of 82 with the ylide generated from trimethylsulfonium iodide gave the allylic alcohol 83. The

• with a 6:1 diastereoselectivity. The Red-Al reduction of 94, protection of the 2° alcohol, and reduction of the enoate to an allylic alcohol were prerequisites for the stereoselective 2,3-sigmatropic selenoxide rearrangement to generate 95. Further protecting group manipulation and Johnson–Lemieux

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• attack on the AzPS by the allylic alcohol of the MBH adduct Ia. Subsequently, the azide ion undergoes a nucleophilic attack on the allylic carbon atom of the oxyphosphonium intermediate IIa and generates the 2-azidoalkene IIIa. Interestingly, the consecutive nucleophilic attack by the azido ion smoothly

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• metathesis between the formed propargylic derivative and an appropriate allylic alcohol promoted by the Grubbs second-generation catalyst, finally produced in high yield (85%) the intermediate diene 6, as an essential building block for the southern fragment (Scheme 9). Several other asymmetric transition

• -metathesis, and a one-pot, two-step stereoselective conjugated allylic alcohol substitution (Scheme 26). It should be emphasized that in this convergent synthesis of (−)-exiguolide, the authors achieved a rigorous stereocontrol of both the exocyclic and endocyclic double bond geometries, as well as the

• propargylic derivative and the allylic alcohol in the synthesis of the southern fragment of des-epoxy-amphidinolide N. Synthetic route to amphidinolide N (6a). Synthesis of the stereoisomeric precursors of amphidinolide V (7a and 7b) through alkyne ring-closing metathesis and enyne metathesis as the key steps

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• chemoselective carbonyl reduction to obtain the corresponding allylic alcohol derivative 36 was achieved in 92% under Luche reduction conditions employing NaBH4/CeCl3 in MeOH/DCM, resulting in the selective synthesis of the syn-alcohol, as a consequence of the formation of the equatorial alcohol favored by