Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• the oxidation of cyclopropanes by oxygen in the presence of transition-metal salts as the catalysts. The reactions of bicycloalkanols 10a–e with singlet oxygen in the presence of catalytic amounts of Fe(III) acetylacetonate produce peroxides 12a–e, which can also be synthesized starting from silylated

• %. Trifluoromethyl-containing dioxolane 25 (Figure 3) was synthesized according to this method in 40% yield [239]. A series of 1,2-dioxolanes 27a–e containing various functional groups R were prepared by the oxidation of cyclopropanes 26a–e (Scheme 9, Table 4). The reaction was performed in the presence of Ph2Se2

• (10 mol %) and azobisisobutyronitrile (AIBN, 8 mol %) in air under irradiation for two days. The product was purified by flash chromatography to obtain a mixture of cis and trans isomers, whose ratio depends primarily on the nature of the substituent in cyclopropanes 26a–e [240]. The oxidation of

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• initialize radical polymerization of HEA. Because of ring strain, cyclopropanes are prone to ring opening via cleavage of one of the three C–C bonds. The resulting reactive intermediates have been shown to participate in a number of synthetic/mechanistic applications [103][104]. One of these applications is

Facile synthesis of functionalized spiro[indoline-3,2'-oxiran]-2-ones by Darzens reaction

• Qin Fu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 918–924, doi:10.3762/bjoc.9.105

• phenacyl bromides and report the facile synthesis of versatile spiro[indoline-3,2'-oxiran]-2-ones. Results and Discussion In recent years we have found that pyridinium salts react with versatile reactive methylene compounds to give different kinds of products, including functionalized cyclopropanes, 2,3

Synthesis of skeletally diverse alkaloid-like molecules: exploitation of metathesis substrates assembled from triplets of building blocks

• Sushil K. Maurya,
• Mark Dow,
• Stuart Warriner and
• Adam Nelson

Beilstein J. Org. Chem. 2013, 9, 775–785, doi:10.3762/bjoc.9.88

• competed with the expected metathesis cascade process. Finally, it was demonstrated that the metathesis products could be derivatised to yield the final products. At each stage, purification was facilitated by the presence of a fluorous-tagged protecting group. Keywords: alkaloids; cyclopropanes

• cyclopentene did not participate in the metathesis reaction, and the bridged macrocycle 53 was obtained in low yield. We have previously observed the formation of macrocyclic metathesis products in similar metathesis cascade reactions [14]. The formation of the cyclopropanes 46 and 47 as byproducts in the

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• stabilized by coordination with a Lewis-basic substituent, react with different electrophiles in a highly diastereoselective manner. On the other hand, when acetals derived from cinnamyl alcohols are used as substrates, cyclopropanes 6 can be obtained in high enantiomeric excess by warming the reaction

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• structures, see Figure 16) were inert to the ylide 21 [49]. When we combined the pregenerated iminium salts 3a–e with the sulfur ylide 21, the expected cyclopropanes 23 were indeed formed in good yield, although with low diastereo- and enantioselectivity (Figure 14) [64]. Even the rate constants calculated

Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

• Bo Leng,
• Stephanie Chichetti,
• Shun Su,
• Aaron B. Beeler and
• John A. Porco Jr.

Beilstein J. Org. Chem. 2012, 8, 1338–1343, doi:10.3762/bjoc.8.153

• cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I)-mediated cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II)-catalyzed enyne cycloisomerization. Keywords: chemical

• yield (Table 1, entry 1). m-Methyl- and naphthyl-containing substrates 10 and 12 afforded polycyclic cyclopropanes 11 and 13 in 48 and 51% yields, respectively (Table 1, entries 2 and 3). We next explored substitution of the pendant alkyne. Reaction with cyclohexane diyne 14 afforded the fused

• water to afford the observed isochromane 23. Conclusion We have described sequential cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes. The reaction sequence involves initial Cu(I)-mediated cycloisomerization/nucleophilic addition to an isochromene followed

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• scCO2 than that achieved for methylene chloride (DCM) (1402 g·L−1 versus 836 g·L−1). It is noteworthy that this higher volumetric productivity was obtained in a shorter time, 165 min for scCO2 compared with 540 min for DCM. Hence, in scCO2 up to 1.5 mmol of cyclopropanes per hour can be obtained

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• bicyclic cyclopropanes. Cycloisomerization reaction of nitrogen- and oxygen-linked 1,6-enynes 1a and 2a. Cycloisomerization reaction of nitrogen- and oxygen-linked 1,6-enynes. Supporting Information Supporting Information File 182: Spectral data. Acknowledgements This work was supported by the Centre

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride

• Sergei I. Kozhushkov,
• Alexander F. Khlebnikov,
• Rafael R. Kostikov,
• Dmitrii S. Yufit and
• Armin de Meijere

Beilstein J. Org. Chem. 2011, 7, 1003–1006, doi:10.3762/bjoc.7.113

• hydrochloride (4·HCl) in 87% yield. Keywords: amines; building blocks; carboxylic acids; Curtius degradation; cyclopropanes; Introduction Several recent patent applications have stirred an increasing interest in research departments of pharmaceutical and agrochemical companies concerning 1- and 2-substituted

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• vinyl alkynyl cyclopropanes 85 to give arenes 86, 87 and cycloheptatriene 88 derivatives through 5-endo-dig and 6-endo-dig cyclization reactions, respectively, under careful control of the reaction conditions (Scheme 25) [58]. A mechanistic rationale for these transformations is shown in Scheme 26

• . Cyclopropanes 85a are generated in situ by intermolecular cyclopropanation of enyne 84 and a carbene resulting from the rearrangement of propargyl ester 83. When tertiary propargyl esters are used, the 5-endo-dig cyclization generates the carbocation 89. Migration of the pivaloyloxy group affords the allylic

• -catalyzed synthesis of ventricos-7(13)-ene. 1,2- vs 1,3-Carboxylate migration. Gold-catalyzed cycloisomerization of vinyl alkynyl cyclopropanes. Proposed mechanism for the cycloisomerization of vinyl alkynyl cyclopropanes. Gold-catalyzed 1,2-acyloxy rearrangement/cyclopropanation/cycloisomerization cascades

Gold-catalyzed naphthalene functionalization

• Pedro J. Pérez,
• M. Mar Díaz-Requejo and
• Iván Rivilla

Beilstein J. Org. Chem. 2011, 7, 653–657, doi:10.3762/bjoc.7.77

• are formed quantitatively. The use of the gold analogue also induces the formation of such fused cyclopropanes in addition to the products derived from the formal insertion of the carbene units into the C–H bonds of naphthalene. The system is completely chemoselective with regards to arene

Bis(oxazolines) based on glycopyranosides – steric, configurational and conformational influences on stereoselectivity

• Tobias Minuth and
• Mike M. K. Boysen

Beilstein J. Org. Chem. 2010, 6, No. 23, doi:10.3762/bjoc.6.23

• induction of the ligand in the cyclopropanation reaction: ee for 3-O-Piv 3c < 3-O-Bz 3b < 3-O-Ac 3a < 3-O-Formyl 26. Thus, of all carbohydrate-derived bis(oxazolines) prepared by us, ligand 26 led to the best enantioselectivities for cyclopropanes trans 6 and cis 6. Conclusion We have prepared new

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• at the stage of the benzazocenol or at an earlier intermediate would constitute a major breakthrough. 3.4. Danishefsky. Homoconjugate addition The homoconjugate opening of activated cyclopropanes has been studied by many groups, utilizing all kinds of nucleophiles [67][68][69][70]. Although this

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• , react with CH2I2/Me3 Al at low temperature (-60°C to room temperature, then 48 h at r.t.) giving spiro-cyclopropanes 35–39 containing the spiro[2][4]heptanol moiety (Scheme 7). [20] High levels of stereoselectivity were found in all the examples studied. Formation of the spirocycle proceeds by a two

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans

• Satish C. Gupta,
• Mandeep Thakur,
• Somesh Sharma,
• Urmila Berar,
• Surinder Berar and
• Ramesh C. Kamboj

Beilstein J. Org. Chem. 2007, 3, No. 14, doi:10.1186/1860-5397-3-14

• ), followed by 1,5-H migration in 8a. [21] The spiropyrans 6 (R = H) bearing cyclopropanes are the secondary photoproducts formed as a result of the further reorganization of 5 (R = H), through a ring contraction-ring expansion mechanism. [22][23] The formation of acetylcyclopropane compound 7 (R = CH3) from

• that of the formation of 5 (R = CH3) from 2 (R = CH3). Regarding the stereochemical disposition of H-11b and H-3a in 5, both of them are cis placed (J = 9.6–9.9 Hz, Ø = 19.2°); in photoproducts bearing cyclopropanes [21]6 (R = H) or 7 (R = CH3), H-1 is trans to H-2 and H-3 (J1,2 = 4.8 Hz, J1,3 = 3.6 Hz