N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• available precatalyst 3a (Figure 2) and K2CO3. Gratifyingly, when ethyl N-PMP-2-iminoacetate (4) was used as acyl anion acceptor [44], the reaction proceeded smoothly in THF at room temperature to generate the desired product 5a in 58% yield (Table 1, entry 1). Surprisingly, no benzoin 6 arising from homo

• -coupling of 1a was obtained. Encouraged by this result, we then attempted the other precatalysts 3b–e depicted in Figure 2. Imidazolium salt 3b and simple triazolium salt 3c gave no coupled product 5a (Table 1, entries 2 and 3). Further screening revealed that bicyclic triazolium salt 3d could catalyze the

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

• Marco Blangetti,
• Patricia Fleming and
• Donal F. O'Shea

Beilstein J. Org. Chem. 2011, 7, 1249–1254, doi:10.3762/bjoc.7.145

• ]. We envisaged that our LiNK metalation conditions with in situ oxidative coupling could offer a facile general approach to [2.2]metacyclophanes, which would be of general synthetic interest (Scheme 2). Oxidative homo-coupling of benzyl anions has previously been noted, but it has remained relatively

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• transmetalation of the aryl group from lithium to iron followed by reductive elimination of the homo-coupling product seems to be plausible, while a similar mechanism is proposed for homo-coupling of organomagnesium compounds with FeCl3 [19][20]. The regiospecificity of the coupling is consistent with this

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

• . reported a general gold-catalyzed direct oxidative homo-coupling of non-activated arenes 207 (Scheme 38). The reaction protocol tolerates a wide range of functional groups [92]. All halogens survive the reaction, which provides the potential for further reactions. 4.2 Rearrangements and ring enlargement A

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• [25] – only 30% yield beside the undesired homo-coupling product 17. A modified and palladium free procedure, however [26], resulted – after acidic workup liberating the aldehyde group – in a satisfactory yield of the mixed tolane 16 as the a-b-c precursor (Scheme 4). Two different building blocks 22

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• performed using a 1:1 substrate ratio with 67% conversion to the desired 4-methoxybiphenyl. The production of biphenyl as a homo-coupling product was also observed in a significant amount of approximately 20% of the final mixture. Indeed, the problem of homo-coupling was encountered in earlier publications

• -methoxybiphenyl yield. A comparative study of 1:1 and 1:2 of 4-bromoanisole to phenylmagnesium chloride was then undertaken in a batch process and the production of biphenyl as well as 4,4′-dimethoxybiphenyl was monitored. The nickel complex catalyst instigates the homo-coupling of the Grignard reagent, in this

Reduction of arenediazonium salts by tetrakis(dimethylamino)ethylene (TDAE): Efficient formation of products derived from aryl radicals

• Mohan Mahesh,
• John A. Murphy,
• Franck LeStrat and
• Hans Peter Wessel

Beilstein J. Org. Chem. 2009, 5, No. 1, doi:10.3762/bjoc.5.1

• donor in specific organometallic reactions, such as the chromium-mediated allylation of aldehydes and ketones [54][55] and the palladium-catalyzed reductive homo-coupling of aryl halides to afford the corresponding biaryls [56][57][58][59] illustrate further versatility of the reagent. The fact that

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

A convenient catalyst system for microwave accelerated cross- coupling of a range of aryl boronic acids with aryl chlorides

• Matthew L. Clarke,
• Marcia B. France,
• Jose A. Fuentes,
• Edward J. Milton and
• Geoffrey J. Roff

Beilstein J. Org. Chem. 2007, 3, No. 18, doi:10.1186/1860-5397-3-18

• ). Buchwald and co-workers have previously noted the failure of 2,4,6-trifluorophenyl boronic acid to react with aryl chlorides, although the origin of this effect was not identified. The origin of this low reactivity could be due to slow transmetalation, [35][36][37][38] homo-coupling problems,[39] or Pd