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

• . Unexpectedly, olefin isomerization occurred which led to the formation of brevipolides M (13) and N (15) after treatment with titanium tetrachloride in ≈85% yield each. Biological activities The extracts of Hyptis brevipes Poit. have been utilized by humanity across the world in tropical regions ranging from

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• diastereoselectivity in the synthesis of bicyclic compounds (dr > 20:1, Scheme 19, 37d, 37e, and 37g). Substrates containing Lewis base moieties (Scheme 19, 36k) were tolerated in the reported reaction conditions, thereby representing a synthetic gain over other olefin isomerization methodologies. An important feature

• cycloisomerization of diolefins triggered by the MHAT process. Some challenges associated with the development of these reactions were the reversible nature of the HAT and the competition with linear isomerization and reductive pathways (Scheme 18) [72][73]. In 2014, the Shenvi group developed an olefin

• isomerization protocol triggered by an MHAT process using salen cobalt complexes as catalysts to furnish isomerized and cycloisomerized products (Scheme 19) [72]. Five and six-membered carbocycles containing quaternary carbon centers were synthetized in good to excellent yields and with excellent

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• proved to transfer the triplet state energy more efficiently than benzaldehyde (8). Furthermore, the triplet state of the carbonyl compound was thought to be the intermediate for both the Paterno–Büchi oxetane formation and the olefin isomerization. Two possible mechanistic pathways for the Paterno–Büchi

• photosensitizers. Salicylaldehyde (68) forms an internal hydrogen bond. Olefin isomerization via energy transfer from a carbonyl compound. Mechanistic pathways for the Paterno–Büchi reaction. Isomeric oxetanes formed after photochemical addition of aryl aldehydes to 2-butenes. Rotation of the C3–C4 bond of the

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• to 1.5 equiv further improved the yield of 3aa to 54% yield (Table 1, entry 4). The moderate yield was attributed to the generation of the olefin isomerization product derived from 1a (vide infra). We then changed the equivalents of reagents 1a and 2a. Although the yield of 3aa was decreased when the

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• second part of their work, they developed adequate conditions to carry out the decyanation reaction without olefin isomerization [18]. They explored several methods for the preparation of 12-butyltricosa-1,22-diene 3 (R = n-C4H9). The reaction was carried out in a slurry of K/Al2O3 in hexane, hexane

• /toluene (1:1) and toluene giving 20%, 63% and 75% of olefin isomerization (from NMR and GC), respectively, for each solvent [34]. This isomerization was attributed to the translocation of the tertiary radical intermediate to a more stable allyl radical leading to the double bond migration. This

• rearrangement was avoided using K/Ph3CH in hexane/ether (3 R = n-C4H9, 41% yield) or K/HMPA/t-BuOH in ether (3 R = n-C4H9, 99% yield). The latter optimized conditions allow the decyanation of alkylcyano α,ω-dienes 2 in quantitative yields with no detection of olefin isomerization (Scheme 3). Radical

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• (MeCN)3PF6-catalyzed variant of the same reaction that proceeds even at room temperature [10]. The ruthenium process differs from the initially-discovered palladium reaction in that it produces cyclic 1,4-dienes exclusively; no olefin isomerization is detected (Scheme 1, path b). Moreover, ruthenium can

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• product observed. In addition, the conjugate enyne could undergo this reaction, giving the interesting electron-rich conjugated diene (6d). In some cases, thermodynamically more stable internal alkenes were also observed along with the kinetic product terminal alkene, likely through olefin isomerization

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• steps involved. All attempts to achieve metathesis on another diene precursor having an endocyclic N-atom (the result of N-alkylation of 77 with 3-iodo-2-(methoxymethyloxy)prop-1-ene) led to either recovery of the starting material or olefin isomerization, even in the presence of a number of ruthenium

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• catalysts was observed for the synthesis of the desired renewable polyesters with molecular weights of up to 17000 Da, which is considerably higher than molecular weights obtained using the same monomer with previously studied catalysts. Moreover, olefin isomerization side reactions that occur during the

• ; metathesis; olefin isomerization; renewable raw materials; ruthenium–indenylidene catalysts; Introduction Among the large number of organic and organometallic reactions allowing the formation of carbon–carbon bonds, olefin metathesis has found its place in organic synthesis as well as polymer science as a

• isomerization is an important side reaction of Ru-catalyzed metathesis reactions. First reports on olefin isomerization claimed that this undesired side reaction was observed on substrates containing allylic oxygen or nitrogen functional groups in combination with first generation catalysts [7][8][9][10][11