Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates

• Julien Lefranc,
• Alberto Minassi and
• Jonathan Clayden

Beilstein J. Org. Chem. 2013, 9, 628–632, doi:10.3762/bjoc.9.70

• carbon atom β to the nitrogen atom [1][2]. The resulting intermediate iminium or N-acyliminium ions are electrophilic, and may themselves trap a nucleophile at the position α to the nitrogen substituent. However, we [3][4] and others [5][6][7] have shown that this typical reactive polarity may be

Synthesis of a library of tricyclic azepinoisoindolinones

• Bettina Miller,
• Shuli Mao,
• Kara M. George Rosenker,
• Joshua G. Pierce and
• Peter Wipf

Beilstein J. Org. Chem. 2012, 8, 1091–1097, doi:10.3762/bjoc.8.120

• , the addition to in situ prepared N-acyliminium species, and ring-closing metathesis (RCM) were key steps in the preparation of a tricyclic isoindolinone scaffold. An unusual alkene isomerization process during the RCM was identified and studied in some detail. Chemical diversification for library

• ; epoxide aminolysis; hydrozirconation; isoindolinones; metathesis; N-acyliminium ion; Introduction Isoindolinones represent a common scaffold seen in naturally occurring compounds such as magallanesine [1], lennoxamine [2] and clitocybin A [3], or drug candidates such as pagoclone [4] (Figure 1). These

• synthetic building blocks, a variety of approaches for the preparation of these heterocycles have been explored [11][12][13][14][15][16][17][18]. Previously, we reported on the addition of organometallic reagents to in situ generated N-acyliminium ions [19]. This methodology applies to a variety of

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

• the coupling reactions of N-acyliminium ions produced from 3-hydroxyisoindol-1-ones or 5-hydroxy-1-pyrrol-2-ones with unactivated olefins in the presence of BF3·OEt2 at room temperature. For most of the olefins, the reactions afforded the Csp3–Csp2 cross-coupling products, but for the α-methylstyrene

• and 1-hexene, the Csp3–Csp3 cross-coupling products were obtained. Keywords: 3-(1-alkenyl)isoindol-1-ones; 5-(1-alkenyl)pyrrol-2-ones; coupling reaction; 2,3-dihydro-3-hydroxyisoindol-1-one; 2,5-dihydro-5-hydroxypyrrol-2-one; N-acyliminium ions; Introduction The coupling of alcohols with alkynes

• ]. We have long been interested in the reactions of N-acyliminium ions produced easily by the Brønsted acid and Lewis acid catalyzed dehydroxylation of α-hydroxyamides [12][13][14]. The high electrophilicity of these species is very suitable for electrophilic addition to carbon–carbon multiple bonds

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• three-component process allowing the synthesis of α-substituted amides. This methodology relied on the oxidative addition of an N-acyliminium species, generated in situ from an imine and an acid chloride, to a Pd(0) complex, furnishing a stable chelated palladium adduct 1, which was isolated and fully

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• trapped immediately after generation. In the "cation flow" method, a carbocation is generated continuously in a flow system by low temperature electrolysis. The generation of the cation can be monitored by a FTIR spectrometer in the flow system. The electrochemically generated N-acyliminium ions can then

• the product selectivity. Cycloadditions using the N-acyliminium ions as heterodienes with a variety of dienophiles, such as alkenes and alkynes, give the corresponding [4 + 2] cycloaddition products in high yields [10]. The same authors also reported a successful polymer synthesis using the same

• technique by adding a monomer to the initiator (N-acyliminium ions) followed by micromixing and the addition of the terminator (diisopropylamine) in a subsequent micromixer. This was considered to be a superior technique to the batch method as the molecular weight distribution of the polymer 3 decreased in

A practical route to tertiary diarylmethylamides or -carbamates from imines, organozinc reagents and acyl chlorides or chloroformates

• Erwan Le Gall,
• Antoine Pignon and
• Thierry Martens

Beilstein J. Org. Chem. 2011, 7, 997–1002, doi:10.3762/bjoc.7.112

• addition of aromatic nucleophiles onto N-acyliminium intermediates, formed in situ by reaction of imines with carbonyl-containing electrophiles. In this latter area, several studies have shown that some electron-enriched arenes can be used as nucleophiles and add efficiently onto the iminium carbon, either

Total synthesis of the indolizidine alkaloid tashiromine

• Stephen P. Marsden and
• Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

• -mediated reductive imide-olefin cyclisation [10]. Our own approach [14] utilises an intramolecular addition of an allylsilane to an N-acyliminium ion to deliver the [4.3.0]-azabicyclic (indolizidine) skeleton 2 (Scheme 1), wherein the pendant vinyl group acts as a handle to install the hydroxymethyl

• sidechain found in tashiromine. The synthesis of azabicyclic assemblies by intramolecular allylsilane/N-acyliminium cyclisations was first studied by Hiemstra and Speckamp [16], who prepared their functionalised allylsilane cyclisation precursors (such as 3) by alkylation of cyclic imides with reagent 4 (X

• of the allylsilane to the N-acyliminium ion occurs through a chair-like transition state with the nascent alkene equatorially disposed. All that remained to complete the synthesis of tashiromine 1 was to effect the oxidative cleavage of the C5 vinyl substituent, then carry out a global reduction of

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• of an allylsilane on an N-acyliminium ion. In this paper, we describe the synthesis of racemic indolizidine 167B and chiral indolizidines: (-)-indolizidines 167B, 195B, 223AB, (+)-monomorine, (-)-(3R,5S,8aS)-3-butyl-5-propylindolizidine and (-)-dendroprimine. Next, we relate the synthesis that we

• ] The allylsilyl functional group is a weak carbon nucleophile for trapping N-acyliminium ions, thus providing a useful method for intramolecular carbon-carbon bond formation. [28][29] We have applied this methodology towards the synthesis of indolizidine alkaloids. (vide supra) We describe here a new

• cyclisation of N-acyliminium ion (S)-49. (-)-Lasubine I and (-)-lasubine II were obtained in six steps with overall yields of 7 and 14% respectively. (+)-Subcosine was prepared in seven steps with an overall yield of 9%. These three compounds were obtained with high enantiomeric purity. These results

Generation of pyridyl coordinated organosilicon cation pool by oxidative Si-Si bond dissociation

• Toshiki Nokami,
• Ryoji Soma,
• Yoshimasa Yamamoto,
• Toshiyuki Kamei,
• Kenichiro Itami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2007, 3, No. 7, doi:10.1186/1860-5397-3-7

• " method, which involves the irreversible oxidative generation and accumulation of highly reactive cations in the absence of nucleophiles [1][2][3][4][5]. Heteroatom-stabilized carbocations, such as N-acyliminium ion pools and alkoxycarbenium ion pools have been generated based on oxidative C-H, C-Si, and