Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• -trifluoromethylpropargyl alcohol are very important for the reaction. Li and co-workers developed a chiral phosphoric acid-catalyzed asymmetric remote 1,8-conjugate addition of thiazolones 111 and azlactones 112 to propargyl alcohols 110 for the synthesis of the chiral allenes 113 and 114, respectively. In the presence of

• 1 mol % CPA 24, 5H-thiazol-4-ones 111 and p-quinone methides generated in situ from propargyl alcohols 110 were incorporated and afforded the axially chiral tetrasubstituted allenes 113 with a chiral thiazolone moiety in high yield (65–97%), high enantioselectivity (76 to >99% ee) and

• diastereoselectivity (10:1 to >20:1 dr). In addition, the enantioselective 1,8-conjugate addition of azlactones 112 to para-quinone methides generated in situ from propargyl alcohols 110 were carried out in the presence of 1 mol % chiral phosphoric acid CPA 7 and afforded the chiral allenes 114 in high yields (65–97

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• formation of allylic carbenium ions, such as 103 [81]. α-(Trifluoromethyl)alkynylcarbenium ions It has been reported that the complex of Co2(CO)6 and propargyl alcohols allows the facile generation of the corresponding propargylium ions (Nicholas reaction) in a relatively strong acidic medium (i.e., TFA

• . also investigated the reactivity of a variety of CF3-substituted propargyl alcohols (Scheme 33) [87]. The reactivity of the benzylic (trifluoromethyl)propargyl alcohol 126 strongly depends on the reaction conditions, as allenes 127 or indenes 128 were both obtained under FeCl3 activation. Indeed, with

Facile preparation and conversion of 4,4,4-trifluorobut-2-yn-1-ones to aromatic and heteroaromatic compounds

• Takashi Yamazaki,
• Yoh Nakajima,
• Minato Iida and
• Tomoko Kawasaki-Takasuka

Beilstein J. Org. Chem. 2021, 17, 132–138, doi:10.3762/bjoc.17.14

• utilize 1 by way of a variety of routes [7][8][9][10][11][12][13][14]. Recently, we turned our attention to oxidized propargyl alcohols, namely ynones 2, because of the interesting structure with two strongly electron-withdrawing moieties, resulting in a high electrophilicity. However, only a few methods

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• dipropargyl derivatives 7e and 7f were then treated with different propargyl alcohols 16 in the presence of Wilkinson’s catalyst/Ti(OiPr)4 under ethanol reflux conditions [53] to obtain the corresponding [2 + 2 + 2] cyclotrimerized alcohols 17–19 and 21 in good yields. During the [2 + 2 + 2] cycloaddition of

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• carried out a large-scale one-pot solvent-free synthesis of amides 6a,b starting from propargyl alcohols 7a,b at room temperature (Scheme 4). At the first step, alcohols 7a,b in the reaction with PCl3 were transformed into the corresponding allenes 1a,h. Then, the addition of Brønsted acid (TfOH or H2SO4

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

• Madhu Babu Tatina,
• Xia Mengxin,
• Rao Peilin and
• Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

• δ 6.01 (H2, H3) [19][21]. Using the optimized conditions in Table 1, entry 4, we then examined the substrate scope. Therefore, glucal 1a was reacted with various O-nucleophiles (using primary, secondary, tertiary, allyl, propargyl alcohols and sugars), C-nucleophiles (using trimethylsilyl cyanide

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• . The hydroarylation reaction further extended to pyrroles for selective monoalkenylation using [Cp*Co(CH3CN)3](SbF6)2 as the catalyst [55]. In contrast, branched-selective hydroarylation of terminal alkynes was achieved by Li et al. The addition of arenes 7 to propargyl alcohols, protected propargyl

• , whereas the electronic nature of propargyl alcohols and amines played a key role in the selectivity control during the insertion. Moreover, the control experiments and DFT calculations show that HOPiv played a crucial role in both the C−H activation and the protonolysis step. In 2016, Yu and co-workers

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• bisoxazoline ligand, diazo compounds 42’ with various electron-withdrawing groups were efficiently oxyalkynylated affording highly enantioenriched propargyl esters 44 (Scheme 23). Subsequent reductive cleavage of the ester gave direct access to enantiopure propargyl alcohols. Besides EBX reagents

Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5’-alkynylation

• Raja Ben Othman,
• Mickaël J. Fer,
• Laurent Le Corre,
• Sandrine Calvet-Vitale and
• Christine Gravier-Pelletier

Beilstein J. Org. Chem. 2017, 13, 1533–1541, doi:10.3762/bjoc.13.153

• propargyl alcohols 11–15 (Scheme 2). The aldehydes 6–10 resulting from oxidation with IBX were isolated and directly submitted to Grignard addition without further purification. Grignard reagents were prepared from trimethylsilyl-, triethylsilyl- or triisopropylsilylacetylene and ethylmagnesium bromide in

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• to the displacement of propargyl alcohols with thiols [18]. Heterogeneous systems are very rare. Corma and Sabater used a heterogeneous system based on palladium on magnesium oxide under borrowing hydrogen conditions [19]. The reaction has to be carried out at 180 °C under N2 in trifluorotoluene with

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

• both the (R)- and the (S)-propargyl alcohols, the CpRu-sulfoxide catalyst prefers to place the stereocenter away from the steric bulk of the sulfoxide (anti configuration). Both syn configurations are disfavored, but the syn-(R)-configuration is energetically more taxing than the syn-(S)-configuration

• more amenable to a wider range of groups on nitrogen, though a significant solvent effect was still observed in these cases. The mechanism of the reaction was then probed by performing the redox isomerization reaction on enantioenriched propargyl alcohols. While a significant matched/mismatched effect

• asymmetric redox bicycloisomerization of 1,6- and 1,7-enynes. This complex was used to synthesize a broad array of [3.1.0] and [4.1.0] bicycles. Sulfonamide- and phosphoramidate-containing products could be deprotected under reducing conditions. Catalysis performed with enantiomerically enriched propargyl

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• : carbocationic rearrangement; cyclopentenones; furans; propargyl alcohols; Introduction In the course of our medicinal program on a new class of anticancer agents [1][2][3], we developed a novel synthesis of cyclopentenones substituted by three different aryl groups (Scheme 1) [4]. This approach combines a

Tandem Cu-catalyzed ketenimine formation and intramolecular nucleophile capture: Synthesis of 1,2-dihydro-2-iminoquinolines from 1-(o-acetamidophenyl)propargyl alcohols

• Gadi Ranjith Kumar,
• Yalla Kiran Kumar,
• Ruchir Kant and
• Maddi Sridhar Reddy

Beilstein J. Org. Chem. 2014, 10, 1255–1260, doi:10.3762/bjoc.10.125

• herein report a synthesis of 1,2-dihydro-2-iminoquinolines (tauromerized form of 2-sulfonylaminoquinolines) from 1-(o-acetamidophenyl)propargyl alcohols via copper-catalyzed ketenimine formation with various sulfonyl azides. 2-Aminoquinolines and their derivatives have been found to be important

• materials were selected with the variation in substitution on propargyl alcohols as well as sulfonyl azides. It was found that the cascade process was applicable for a wide range of substrates providing the dihydroquinoline derivatives 9 in yields ranging from 36% to 77% (Scheme 3). Initially, we screened 2

• -propargyl alcohols prepared from aminobenzaldehydes as they were unreactive in Wang's protocol. Thus, 2a was treated with various sulfonyl azides. Trifluoromethanesulfonyl azides reacted similar to toluenesulfonyl azide to afford the products 9b and 9c in 71% and 55% yields. The lower yield in case of 9c

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• hydrophosphination of propargyl alcohols [242]. Several catalytic systems were tested and the reaction with 5 mol % RuCl(cod)(C5Me5) in the presence of Na2CO3 provided the best results (Scheme 39). The reaction gave two stereoisomeric adducts (Z)-133 and (E)-133. The hydrophosphination of 132 proceeded with

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

• G. Gangadhararao,
• Ramesh Kotikalapudi,
• M. Nagarjuna Reddy and
• K. C. Kumara Swamy

Beilstein J. Org. Chem. 2014, 10, 996–1005, doi:10.3762/bjoc.10.99

• G. Gangadhararao Ramesh Kotikalapudi M. Nagarjuna Reddy K. C. Kumara Swamy School of Chemistry, University of Hyderabad, Hyderabad 500 046, A. P., India. Fax: (+91)-40-23012460 10.3762/bjoc.10.99 Abstract A range of phosphinoylindoles was prepared in one-pot from functionalized propargyl alcohols

• ; propargyl alcohols; Introduction Allenes, by virtue of cumulative double bonds that facilitate reactions with diverse classes of substrates, are versatile building blocks from a synthetic perspective [1][2]. They are also found in many natural products, pharmaceuticals [3] and molecular materials [4]. Thus

• allenylphosphine oxides/allenylphosphonates. Results and Discussion In order to achieve the anticipated phosphinoylindoles/isocoumarins, we prepared a variety of functionalized propargyl alcohols 1a–m and 2a–j containing an acetamide, benzamide or an ester group at the ortho position (Figure 1) [35][36][37]. Some

A concise synthesis of 3-(1-alkenyl)isoindolin-1-ones and 5-(1-alkenyl)pyrrol-2-ones by the intermolecular coupling reactions of N-acyliminium ions with unactivated olefins

• Nianhong Lu,
• Lihong Wang,
• Zhanshan Li and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 192–200, doi:10.3762/bjoc.8.21

• , aromatics and active methylene compounds has attracted great attention in recent years as an effective and environmentally benign strategy for the construction of carbon–carbon bonds with the concomitant loss of water. For example, the metal-catalyzed coupling of allyl, benzyl, and propargyl alcohols with

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

• available heteroatom-substituted propargyl alcohols 10 has been developed by Aponick and co-workers [22]. For the formation of tetrahydropyran analogs 13 and 15, the gold(I)-catalyzed cyclization of monoallylic diols 12 and 14 is an efficient method (Scheme 2) [23][24]. In addition to common organic

• enriched secondary propargyl alcohols led to the chiral oxetan-3-one with no apparent racemization (Scheme 20). 3 Gold-catalyzed C–N bond formations Many organic compounds containing nitrogen exhibit important biological and pharmaceutical properties. As with gold-catalyzed C–O bond formation, the directly

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• . Direct propargylic substitutions: Scope of nucleophiles. Meyer–Schuster rearrangements. Silyl-protected propargyl alcohols in propargylic substitutions. Acetylacetone as nucleophile in direct propargylic substitution. Enantiomerically enriched propargylic alcohols. Scope of ‘activated’ alcohols in direct

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• –Crafts alkylation; green chemistry; hydroalkylation; hydroarylation; Lewis-acid catalysis; propargyl alcohols; Introduction In 1887 Charles Friedel and James Mason Crafts isolated amylbenzene after the treatment of amyl chloride with AlCl3 in benzene (Scheme 1) [1]. This was not only one of the first

• , lower toxicity, and the fact that only stoichiometric amounts of water are generated as the side product the FC alkylation with benzyl-, allyl- and propargyl alcohols presented a first and important step toward an environmental friendly process. In 1986, Uemura et al. investigated the chlorination of

• propargyl alcohols 16 as alkylating reagents represented a valuable advancement (Scheme 8) [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. An example of this procedure represents the effective iron(III)-catalyzed one-step synthesis of phenprocoumon (20), an anticoagulant of the