Total synthesis of (+)-grandiamide D, dasyclamide and gigantamide A from a Baylis–Hillman adduct: A unified biomimetic approach

• Andivelu Ilangovan and
• Shanmugasundar Saravanakumar

Beilstein J. Org. Chem. 2014, 10, 127–133, doi:10.3762/bjoc.10.9

• (14) [11]. In order to reduce the amount of acrylate and to increase the yield of compound (±)-16, the Baylis–Hillman reaction between the aldehyde 14 and ethyl acrylate (15) was tried using different catalysts such as DBU, quinuclidine [12] and n-Bu3P. DABCO was found to be a better catalyst and the

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• scientists and consists of a chiral hydroisoquinoline linked to a (R)-quinuclidinol unit through a carbamate linkage (Figure 6). Upon protonation the tertiary amine of the quinuclidine is expected to resemble the ammonium substructure of muscarine (2.58) [76]. This molecule can be prepared by direct coupling

• racemic quinuclidinol. However, an improved approach makes use of a Noyori-type asymmetric reduction employing a BINAP ligated RuCl2 and a chiral diamine to yield the desired (R)-quinuclidine in high yield and enantioselectivity [78]. The enantioselective synthesis of the tetrahydroisoquinoline fragment

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• traditional stirring proceeds at a slower reaction rate as compared to ball-milling [47]. The transition state (TS 4) for this transformation involves a hydrogen-bonded ternary complex of catalyst and substrates in which two NH groups of the squaramide moiety activate the nitroalkene and the quinuclidine

Reactions of nitroxides XIII: Synthesis of the Morita–Baylis–Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

• Jerzy Zakrzewski

Beilstein J. Org. Chem. 2012, 8, 1515–1522, doi:10.3762/bjoc.8.171

• aldehydes. Keywords: 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl; DABCO; Morita–Baylis–Hillman reaction; nitroxides; quinuclidine; Introduction In the Morita–Baylis–Hillman (MBH) reaction, aldehydes react with a double bond activated by an electron-withdrawing group (EWG). The vinylic carbon

• bearing an EWG undergoes substitution. The reaction is carried out in the presence of either a tertiary amine (e.g., DABCO [2][3][4][5][6], quinuclidine and its derivatives [7][8][9][10][11][12], DBU [13][14], DBN [13], DMAP and its derivatives [4][15][16], urotropine [17], brucine N-oxide [18]) or a

• obtain a compound bearing both nitroxyl and ferrocenyl moiety) ferrocenyl aldehyde (4o). Two catalytic systems were tested: DABCO, and quinuclidine with methanol as a cocatalyst. The latter system was chosen because it has been described as an excellent rate enhancer for the MBH reaction [9][11

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• simultaneously coordinates electrophilic unsaturated 1,4-diketone via hydrogen bonding and activates the nucleophilic malonate via the tertiary amine of the quinuclidine moiety. Due to the symmetry of the substrate, there is no regioselectivity problem. A face selection is determined by the different access of

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• to the respective mono-substituted amine (e.g., NMe2n-Pr (27) with MCA(27) = 552.1 kJ/mol). However, even in systems with linear alkyl substituents unfavorable steric effects appear to exist between the alkyl substituents, and confining the alkyl groups to a bicyclic cage structure as in quinuclidine

• –N distance in pyridine-trityl adduct (1TT), which amounts to 1.57 Å, can be used. A slightly increased C–N bond length can be found for the TCA-adduct of quinuclidine 53 (1.76 Å), which is in distinct contrast to the structurally similar DABCO. It should be added that all other electrophiles

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• (tetrafluoroborate); TEDA = triethylenediamine) [27][28][29] marked some important discoveries: First, a new generation of highly enantioselective chiral fluorinating reagents, derived by fluorine transfer [30] from F–TEDA to the quinuclidine portion of cinchona-alkaloids, was introduced by the groups of Cahard [31

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32