Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• used for consecutive double [4 + 2] cycloaddition reactions [2][3][4] to provide a rapid access to polycyclic carbon frameworks. Thus, a number of methods for the preparation of the parent 3-methylenepenta-1,4-diene [5] and its substituted derivatives [6][7][8][9][10][11][12][13][14][15][16][17] has

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• cycloaddition reactions exist, they rely on intramolecular azide delivery under thermal conditions [15][16][17][18][19][20][21]. Examples of substrate control in an acid-catalyzed intermolecular reaction of azides with alkenes are limited [22]. We report our initial study of the intermolecular

• , diastereoselective sequence of two [3 + 2] cycloaddition reactions promoted by triflic acid where the large 1,3-diol protecting group – the 1,1,3,3-tetraisopropoxydisiloxanylidene group (TIPDS) – plays a crucial role in facial discrimination. Results and Discussion Our approach to the preparation of enantiomerically

Acid catalyzed cyclodimerization of 2,2-bis(trifluoromethyl)-4-alkoxy-oxetanes and -thietanes. Synthesis of 2,2,6,6-tetrakis(trifluoromethyl)-4,8-dialkoxy-1,5-dioxocanes and 3,3,7,7-tetrakis(trifluoromethyl)-9-oxa-2,6-dithia-bicyclo[3.3.1]nonane

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2010, 6, No. 46, doi:10.3762/bjoc.6.46

• process itself is simple, reproducible and provides easy access to this new group of stable polyfluorinated 1,5-dioxocanes. It should also be pointed out, that examples of electrophilic [4 + 4] cycloaddition reactions are extremely rare and limited to two examples: the reaction of the oxetane (derived

An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives

• Rajeshwar Reddy Sagyam,
• Ravinder Buchikonda,
• Jaya Prakash Pitta,
• Himabindu Vurimidi,
• Pratap Reddy Padi and
• Mahesh Reddy Ghanta

Beilstein J. Org. Chem. 2009, 5, No. 66, doi:10.3762/bjoc.5.66

• acid hydrazide with 3-bromo-1,1,3-tricyano-2-phenylpropene [17]; and the reaction between 3-chloropyridazines with propargylic alcohol in the presence of Pd(PPh3)2Cl2–CuI with diethylamine as the reaction medium [18][19]. The second approach is based on cycloaddition reactions, such as the

Synthesis and Diels–Alder cycloaddition reaction of norbornadiene and benzonorbornadiene dimers

• Bilal Nişancı,
• Erdin Dalkılıç,
• Murat Güney and
• Arif Daştan

Beilstein J. Org. Chem. 2009, 5, No. 39, doi:10.3762/bjoc.5.39

• indistinguishable. To determine which is which, cycloaddition reactions of dimers are more informative. Dimers 7 and 16 give symmetric addition products 11, 12 and 18, 19, whereas the reaction of dimers 8 and 17 resulted in the formation of unsymmetrical products 13, 14 and 20, 21. For the symmetric addition

• ). Numbering of carbon atoms and description of possible structures for dimers 11–14 and 18–21. Synthesis of starting materials 4 and 5. Synthesis and Diels–Alder cycloaddition reactions of dimers 7 and 8. Synthesis and Diels–Alder cycloaddition reactions of dimers 16 and 17. Acknowledgments This work has

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl- 3-methylsulfanyl- 2-tosylpyrroles from aroylketene dithioacetals and TosMIC

• H. Surya Prakash Rao and
• S. Sivakumar

Beilstein J. Org. Chem. 2007, 3, No. 31, doi:10.1186/1860-5397-3-31

• heterocyclic systems, examples of their participation in the cycloaddition reactions are rare. In continuation of our interest on ketene acetals [5][6][7] we considered that 1,3-dipolar cycloaddition of the anion generated from the von Leusen's reagent (p-tolylsulfonyl)methyl isocyanide (TosMIC) 2 to AKDTAs 1

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• has shown that for cycloaddition reactions to occur, the non-reactive substituents around the silicon centre must be more bulky than the Me or Ph groups employed in these studies. Denmark's work demonstrated that the angles at the silicon centre between the two 'arms' of the silyl ether can be up to

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• , usually AlCl3, could be used to enhance the reactivity of these poor dienophiles. [1][2][3][4] Particularly the cycloenones are desirable dienophiles, because their cycloaddition reactions are a remarkable tool for the synthesis of octalones and related bicyclic olefinic ketones (e.g., decaline-based

• attack. The resulting lowering of the activation energy usually leads to an enhancement of stereo- and regioselectivity [7]. It was also soon realized that the modifications in the cycloaddition reactions parameters should depend on the Lewis acids used, and a number of authors have performed comparison