Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• variety of methods for enantioselective syntheses of structurally diverse acyclic, carbocyclic, and heterocyclic compounds. 2.1 [3 + 2] Annulation of allenes with activated alkenes Nucleophilic phosphine-catalyzed annulations have been established as very useful tools for the syntheses of carbo- and

• binaphthyl skeleton, Fu and co-workers developed the first asymmetric [3 + 2] annulation of ethyl allenoate with various α,β-unsaturated enones to provide functionalized cyclopentenes (Scheme 2) [35]. The key structural feature of the chiral catalyst B1 is its rigid binaphthyl skeleton. This approach allowed

• spirocyclic compounds containing two neighboring quaternary and tertiary stereocenters in modest to excellent yields (up to 97%) and high enantioselectivities (up to 95% ee). Subsequently, the Fu group applied this approach to the [3 + 2] annulation of allenes with 1,1-disubstituted olefins to synthesize

Visible light mediated intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes

• Theresa H. Nguyen,
• Soumitra Maity and
• Nan Zheng

Beilstein J. Org. Chem. 2014, 10, 975–980, doi:10.3762/bjoc.10.96

• Theresa H. Nguyen Soumitra Maity Nan Zheng Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA 10.3762/bjoc.10.96 Abstract Intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes is realized using visible light photoredox catalysis

• synthetic potential of amine radical cations [21][27][28]. One of the reported methods from our group involves [3 + 2] annulation of cyclopropylanilines with alkenes [29]. We were intrigued by the possibility of extending this annulation method to include alkynes. The immediate benefits of using alkynes

• intermolecular [3 + 2] annulation of monocyclic cyclopropylanilines with alkynes under visible light photoredox conditions. Results and Discussion Biphenylcyclopropylamine 1 and phenylacetylene (2) were chosen as the standard substrates to optimize the catalyst system for the [3 + 2] annulation with alkynes

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• ) followed by oxidative coupling of the formed alkylgold moiety with the ortho C–H bond of the tethered phenyl group. Compound 137 was finally obtained via reductive elimination of intermediate 141 (Scheme 34). The formal [3 + 2] annulation between the aniline moiety and the C–C double bond constitutes the

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

• (distonic ion) [106]. We have applied Ru(bpz)3(PF6)2-catalyzed photooxidation of N-cyclopropylanilines to induce this rearrangement reaction. The resulting distonic ion was then intercepted by alkenes to produce [3 + 2] annulation products (Scheme 32) [107]. An aryl group on the amine was required for the

• azodicarboxylates. α-Arylation of amines. Plausible mechanism for α-arylation of amines. Photoinduced C–C bond cleavage of tertiary amines. Photoredox cleavage of C–C bonds of 1,2-diamines. Proposed mechanism photoredox cleavage of C–C bonds. Intermolecular [3 + 2] annulation of cyclopropylamines with olefins

• . Proposed mechanism for intermolecular [3 + 2] annulation. Photoinduced clevage of N–N bonds of aromatic hydrazines and hydrazides.

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• of Chemistry & Molecular Engineering, East China University of Science and Technology, and 130 MeiLong Road, Shanghai 200237, People’s Republic of China 10.3762/bjoc.8.121 Abstract We have developed a multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman

• previous literature. Keywords: asymmetric [3 + 2] annulation; maleimides; Morita–Baylis–Hillman carbonates; multifunctional thiourea-phosphine; organocatalysis; Introduction Highly functionalized cyclopentene derivatives are important subunits in a variety of biologically active molecules and have

• attracted the broad attention of synthetic and pharmaceutical chemists [1][2]. Among numerous synthetic approaches, phosphine-mediated [3 + 2] annulation of electron-deficient olefins is an efficient method to construct this interesting structural motif [3][4][5][6][7][8][9][10]. According to the pioneering

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• ) catalyst is able to activate these allenic intermediates in situ, triggering a stepwise intramolecular (3 + 2) annulation reaction with the pendant alkene. This cycloaddition provides a cyclic gold carbene species XXV, which is eventually transformed into the final bicyclic adduct by a 1,2-hydrogen shift

• ethers and alkenes (MOM = methoxymethyl, Scheme 25) [90]. The activation of these allenes by the dichloro(pyridine-2-carboxylato)Au(III) complex Au7 generates an oxocarbenium intermediate XXVII, which undergoes the (3 + 2) annulation with the alkene. The resulting bicyclo[3.1.0] species XXVIII, related

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• data (1H and 13C NMR) of synthetic asimicin was identical to those of naturally occurring compounds. In 2005, Roush’s group synthesized the bis-THF core of asimicin [98] from two sequential chelate-controlled [3+2] annulation reactions of allylsilanes and appropriately substituted aldehydes (Scheme 38

• ). Subjecting the protected allylsilane 281 to the [3+2] annulation reaction with α-benzyloxyacetaldehyde (282) afforded the 2,5-trans-THF 283. Conversion of 283 to aldehyde 284 was achieved by reductive removal of the benzyl group and subsequent oxidation of the alcohol. Treatment of aldehyde 284 with

• group reported the total synthesis of (+)-bullatacin (311) via a diastereoselective [3+2] annulation reaction (Scheme 43) [104]. Racemic aldehyde 314, which was prepared from allylsilane (±)-312 and α-benzyloxy acetaldehyde (313), was treated with the highly enantiomerically enriched allylsilane 315 in

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• -carbon partners in [3+2] annulation reactions. Thus, reaction with aldehydes,[7] imines/iminiums,[7][8] enones [9][10][11] and nitrosyl cations [12] leads to dihydrofurans, dihydropyrroles, cyclopentenes and isoxazoles respectively.[13] In most cases the silicon is retained in the final product and can