Diels–Alder reactions of myrcene using intensified continuous-flow reactors

• Christian H. Hornung,
• Miguel Á. Álvarez-Diéguez,
• Thomas M. Kohl and
• John Tsanaktsidis

Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15

• continuous flow [22][23]. Over the past years, Diels–Alder reactions of isoprene using laboratory-scale flow reactors were studied by different research groups [24][25]. A continuous-flow reactor can offer a range of benefits over batch processing, with the enhanced heat and mass transfer arguable being one

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• sequential postsynthetic modification of polystyrene by isoprene [16]. The authors focus mainly on the engineering aspects of the project rather than the chemical reaction itself. The first part of the process involves the chemical reaction between styrene and s-BuLi, which is employed as an initiator

• large scale. Furthermore, Höcker et al. report the post polymerisation of polystyrene with isoprene, which is actually carried out in the same processing line as the polymerisation of styrene, i.e., styrene is polymerised initially in the extruder barrel and isoprene is fed into the barrel at a later

• heating (right). Taken from [44]. Synthesis of Ni(NCS)2(PPh3)2 and [Ni(salen)] by twin screw extrusion. Adapted from [2]. Polymerisation of styrene using s-BuLi as an initiator. Telescoping process of the formation of polystyrene, followed by post polymerisation functionalisation with isoprene. The figure

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

• Loïc Leclercq

Beilstein J. Org. Chem. 2016, 12, 2644–2662, doi:10.3762/bjoc.12.261

• are composed of lipids. Lipids also provide various other biological functions, including cell signaling and storage of metabolic energy by lipogenesis. Biological lipids are basically due to two types of compounds acting as “building blocks”: ketoacyl groups and isoprene units. From this point of

• prenols, which are produced from condensation of isoprene units [54]. These compounds can be easily included inside the CDs because they are hydrophobic or amphiphilic molecules. As mentioned earlier, and as it will become exceeding clear throughout the following sections, the majority of research

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• plausible mechanism starts from 4b+· that results in J4+· by inductive cleavage, followed by a neutral loss of isoprene to K4+·. The α-cleavage of J4+· would yield a primary radical, but this can immediately be stabilised if the α-cleavage is coupled with a hydrogen rearrangement to generate the conjugated

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

• Sean P. Bew,
• Glyn D. Hiatt-Gipson,
• Graham P. Mills and
• Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

• 7TJ, UK 10.3762/bjoc.12.103 Abstract Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a ’halide for nitrate’ substitution. Employing readily available starting materials, reagents and Horner–Wadsworth–Emmons chemistry

• studied their ability to undergo an ‘allylic halide for allylic nitrate’ substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates (‘isoprene nitrates’) in 66–80% overall yields. Using NOESY experiments

• the elucidation of the carbon–carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our ‘halide for nitrate’ substitution chemistry we outline the straightforward transformation of (1R,2S)-(−)-myrtenol bromide into the previously unknown

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

• Daria Yu. Dzhons and
• Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

• presence of isoprene as a triplet nitrene quencher. The addition of isoprene lead to a significantly increased yield of 3-amino-6-nitro-2,1-benzisoxazole and an insignificant decrease of the primary amine yield. Thus it was demonstrated that the formation of 3-amino-6-nitro-2,1-benzisoxazole goes through

Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

• Helmut Ritter,
• Monir Tabatabai and
• Markus Herrmann

Beilstein J. Org. Chem. 2016, 12, 245–252, doi:10.3762/bjoc.12.26

• solution of N-bromosuccinimide (NBS, 20 g, 0.12 mol) in 1/3 THF and 2/3 H2O, isoprene was added in 3 small portions of 5 mL (0.05 mol) at 0 °C. Stirring was continued for an additional hour. THF was evaporated and the remaining aqueous mixture was extracted several times with diethyl ether. The extract was

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• trapped by hetero-Diels–Alder reaction with dienes [54][55], and detection of the resulting hetero-Diels–Alder adducts used to confirm the formation of free nitroso intermediates. Thus trapping experiments were conducted using isoprene (14) to investigate the formation of a nitroso species in this

• reaction. First a 1:1 mixture of cycloadducts 15 and 16 was synthesised as a reference sample using Kirby’s conditions for the hetero-Diels–Alder reaction (N-Boc-hydroxylamine (8), isoprene (14) and sodium periodate, Scheme 3a) [54][55]. Then isoprene (14) and N-Boc-hydroxylamine (8) were combined in

• isoprene indicates the relative mildness of these conditions for nitroso formation. Nicholas et al. have reported a similar experiment to study the iron(II,III) chloride-catalysed reaction of N-phenylhydroxylamine with 2,3-dimethyl-1,3-butadiene, in which the Diels–Alder cylcoadduct was not observed, and

SmI₂-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B

• Nils Marsch,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184

• their reductive dimerization. We also describe the synthesis of the antimicrobial natural product indiacen B (2) from the myxobacterium Sandaracinus amylolyticus [5], bearing a unique isoprene moiety chlorinated at the methylene group. Results and Discussion SmI2-induced reductive dimerizations 6

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• target compounds 40 and 41 in 53 and 65% yield, respectively. The synthesis of the second series is shown in Scheme 8 [59]. Amberlyst 15 efficiently catalyzed the condensation of 1,3,5-trihydroxybenzene (29) with isoprene in 53% yield. The following Friedel–Crafts acylation gave the intermediates 43–46

• . Reagents and conditions: (a) acyl chloride, AlCl3, CS2/PhNO2, 55 °, 2 h; (b) geranyl bromide, K2CO3, acetone, reflux, overnight; (c) pTSA, benzene, reflux, 2 h. Synthesis of acylphloroglucinol derivatives 43–51. Reagents and conditions: (a) isoprene, Amberlyst 15, THF/hexane; (b) benzoyl chloride, AlCl3

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• with aryl-substituted 1,3-dienes 1a–k because the use of allylic alcohol itself led to significant lower yields (up to 30%). Only in case of buta-1,3-diene, 2,3-dimethyl-1,3-butadiene and isoprene allyl alcohol could be used directly without decreasing the yield (Table 1, entries 12–14). The results of

• . Electron-withdrawing and electron-donating groups as well as sterically hindered aryl substituents are also accepted (see Table 1, entries 7 and 9). The use of buta-1,3-diene and 2,3-dimethyl-1,3-butadiene gave the 1,4-dienols in excellent yields (Table 1, entries 12 and 13). When isoprene was used, the

Synthesis of isoprenoid bisphosphonate ethers through C–P bond formations: Potential inhibitors of geranylgeranyl diphosphate synthase

• Xiang Zhou,
• Jacqueline E. Reilly,
• Kathleen A. Loerch,
• Raymond J. Hohl and
• David F. Wiemer

Beilstein J. Org. Chem. 2014, 10, 1645–1650, doi:10.3762/bjoc.10.171

• biological activity of these compounds [28]. Such studies are ongoing and will be reported in due course. Inhibitors of isoprene biosynthesis. Biosynthesis of geranylgeranyl diphosphate. A known inhibitor of GGDPS (5) and a new analogue (6). Synthesis of bisphosphonate ethers 6 and 11. Synthesis of prenyl

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• crude TMS enol ether 22 in CH2Cl2 (1.0 mL). The reaction mixture was stirred for 10 min at 0 °C, and then isoprene (39 μL, 0.39 mmol) was added. The resultant solution was concentrated. The residue was roughly purified by flash column chromatography (silica gel 24 g, hexane/EtOAc 1:0 to 10:1) to afford

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• titanium-catalyzed allylmagnesiation of isoprene was reported in the 1970s, the scope of the reagents was limited to the allylic magnesium reagents [145][146]. Recently, Terao and Kambe reported copper-catalyzed regioselective carbomagnesiation of dienes and enynes using sec- or tert-alkylmagnesium

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• step. Neither the 3-deuterio nor the 3,4-dideuterio derivative of the parent system 2 seem to be known. Applying the DMS-approach to either isoprene or 1,3-pentadiene leads to the desired monomethyl derivatives of 2, 3-methyl-1,2,4,5-hexatetraene and 1,2,4,5-heptatetraene, but the yields are poor and

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• , and butyl methacrylate was also copolymerized with 2-aminoethyl methacrylate by the same authors [42]. Cell–particle investigations were performed with polyisoprene and copolymers of styrene and isoprene fluorescent particles. Their uptake was found to be faster in comparison to polystyrene particles

• copolymerization of isoprene afforded low crystalline polymers. After Grubbs popularized water resistant catalysts for metathesis polymerizations, it became clear that metathesis could be also performed in aqueous heterophase systems. Claverie et al. studied the ring-opening metathesis polymerization (ROMP) in

• dimethylformamide in hexane were stabilized by a copolymer surfactant with isoprene and methyl methacrylate blocks. A shell of polymethyl methacrylate could be subsequently added after the polyaddition [111]. One of the techniques associated with step-growth polymerizations is the so-called interfacial polyaddition

End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• , however, to procure this transformation (i.e. 16), that is reaction of isoprene and oxygenated derivatives, with enone 12 completely failed. Davies [16][17], however, demonstrated that a photochemical assisted thermal [4+2] cycloaddition does proceed but with incorrect relative stereochemistry and limited