Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement

• Maroš Bella,
• Bohumil Steiner,
• Vratislav Langer and
• Miroslav Koóš

Beilstein J. Org. Chem. 2014, 10, 1942–1950, doi:10.3762/bjoc.10.202

• Technology, 412 96 Göteborg, Sweden 10.3762/bjoc.10.202 Abstract The Grignard reaction of 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside and benzylmagnesium chloride (or bromide) afforded a non-separable mixture of diastereomeric benzyl carbinols and diastereomeric o-tolyl carbinols. The latter

• possible mechanism for the Grignard reaction leading to the benzyl→o-tolyl rearrangement is also proposed. Keywords: aldehyde; benzyl versus o-tolyl; carbohydrate; Grignard reaction; rearrangement; X-ray crystallography; Introduction One of the most popular synthetic routes leading to the formation of

• possible the preparation of a series of useful carbohydrate derivatives [1][2][3][4][5][6][7][8]. Despite the demonstrable advantages of the Grignard reaction, there remain, in addition to the recognised drawbacks, some new unexpected impediments limiting its application in the synthesis of branched

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

• another internal nucleophile in the same distance (6-membered) as a competitor. Results and Discussion Thus, we synthesized a substrate 3 (from 1 via 2a) through Grignard reaction followed by acetylation (Scheme 2). Substrate 3 contains two nucleophiles in the form of acetyl and acetamide groups at equal

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• derivative with limited stability, which was immediately converted into alcohol 4 by diastereoselective Felkin–Anh type Grignard addition with isopropyl magnesium chloride (50% yield over 2 steps from 3, dr > 95:5). However, we could not confirm that the use of diethyl ether as co-solvent in the Grignard

• reaction would suppress the reformation of alcohol 3 as the competing Grignard reduction product, as it had been claimed by Zhu and co-workers in their initial report [32]. It was therefore decided to attempt the recycling of alcohol 3, which was obtained in varying amounts, for another round of oxidation

Self-assembly of metallosupramolecular rhombi from chiral concave 9,9’-spirobifluorene-derived bis(pyridine) ligands

• Rainer Hovorka,
• Sophie Hytteballe,
• Torsten Piehler,
• Georg Meyer-Eppler,
• Filip Topić,
• Kari Rissanen,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 432–441, doi:10.3762/bjoc.10.40

• . Tour [30], M. Gomberg [31], and V. Prelog [32][33] leading to (rac)-2,2’-dihydroxy-9,9’-spirobifluorene ((rac)-1) in six consecutive steps. This sequence involved a Sandmeyer-like iodination, followed by a Grignard reaction with fluorenone to furnish the corresponding tertiary alcohol. This alcohol was

The total synthesis of D-chalcose and its C-3 epimer

• Jun Sun,
• Song Fan,
• Zhan Wang,
• Guoning Zhang,
• Kai Bao and
• Weige Zhang

Beilstein J. Org. Chem. 2013, 9, 2620–2624, doi:10.3762/bjoc.9.296

• C3 via Grignard reaction, the introduction of the stereogenic center on C2 by Sharpless asymmetric dihydroxylation, the protection of the C1 and C2 hydroxy groups with tert-butyldimethylsilyl trifluoromethanesulfonate (TBSOTf), and the selective cleavage of the primary OTBS ether using catalytic DL

• retrosynthetic analysis of I and I′ is presented in Scheme 1. Diol II and II′ arose from a Sharpless asymmetric dihydroxylation that form the C2 stereogenic center. The installation of the C3 stereocenter on vinyl ether III was proposed to utilize a Grignard reaction followed by chromatographic separation

• set using a Grignard reaction, and the hydroxy group on C2 could be introduced with the correct stereochemistry by performing a Sharpless asymmetric dihydroxylation on vinyl ether 5. In addition, diol 6 was converted to 11 by protection with TBSOTf followed by selective unveiling of the C1 hydroxy

A protecting group-free synthesis of the Colorado potato beetle pheromone

• Zhongtao Wu,
• Manuel Jäger,
• Jeffrey Buter and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2013, 9, 2374–2377, doi:10.3762/bjoc.9.273

• . Although the approach is elegant, (S)-linalool required for natural (S)-1 is not commercially available. In 2005, Mori employing lipase-catalyzed kinetic resolution of (±)-2,3-epoxynerol as the key step, synthesized both (S)- and (R)-1 in gram quantities with high ee. In Chauhan’s work, Grignard reaction

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

• James C. Anderson,
• Andreas S. Kalogirou,
• Michael J. Porter and
• Graham J. Tizzard

Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200

• allow elucidation of the absolute stereochemistry of piperazirum (2). Results and Discussion The common α-keto acid derivative 5 was easily prepared from a Grignard reaction of isobutylmagnesium chloride with diethyl oxalate to give α-keto ester 10 in 94% yield (Scheme 3) [47]. Saponification of 10 with

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium

• Michael Dobmeier,
• Josef M. Herrmann,
• Dieter Lenoir and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36

• techniques. To a slurry of Mg powder (0.67 g, 28 mmol) in dry THF (4 mL), 2 mL of a solution of 2-phenyl-1-bromethane (3.0 mL, 28 mmol) in dry THF (10 mL) was added. The Grignard reaction was initiated by the addition of iodine followed by sonication for several minutes. When the exothermic reaction started

• reaction was carried out under a dry nitrogen atmosphere by using standard Schlenk techniques. A solution (1 mL) of 2-phenyl-1-bromethane (1.35 mL, 10.0 mmol) in dry THF (10 mL) was added to Mg powder (0.25 g, 10 mmol). The Grignard reaction was initiated by the addition of iodine followed by sonication

• -Methoxyphenyl)-2-phenylpropan-1-ol (Table 1, entry 5): The reaction was carried out under a dry nitrogen atmosphere by using standard Schlenk techniques. 1 mL of a solution of 4-bromo-1-methoxybenzene (0.62 mL, 5.0 mmol) in dry THF (10 mL) was added to Mg powder (0.12 g, 5.0 mmol). The Grignard reaction was

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• dihydroxylation with simultaneous deprotection of (+)-22 gave the final product (−)-23 in good yield. In an interesting work by Rao and co-workers [54] a Grignard reaction was employed to design the diene with desired stereochemistry for the synthesis of 1,4-dideoxy-1,4-imino-D-allitol (29) and the formal

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

• by conversion to the epoxide 80. Addition of the C3-C13 fragment in a copper-catalyzed Grignard reaction afforded 81. The butenolide ring in 4,5-dehydro-cis-solamin (83) was put in place using a ruthenium catalyzed Alder-ene reaction of 81 with 82. Final selective reduction of the 4,5-double bond

Development of potential manufacturing routes for substituted thiophenes – Preparation of halogenated 2-thiophenecarboxylic acid derivatives as building blocks for a new family of 2,6-dihaloaryl 1,2,4-triazole insecticides

• John W. Hull Jr.,
• Duane R. Romer,
• David E. Podhorez,
• Mezzie L. Ash and
• Christine H. Brady

Beilstein J. Org. Chem. 2007, 3, No. 23, doi:10.1186/1860-5397-3-23

• /debromination procedure developed for 3-methylthiophene gave 2,4-dibromo-3-methylthiophene, which was a key intermediate for conversion to 4-bromo-3-methyl-2-thiophenecarbonyl chloride 1. Carboxylic acid functionality was introduced either by a Grignard reaction followed by carbonation with CO2, or a palladium

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• impossible, since any attempt to work-up the Grignard reaction resulted in hydrolysis of the silyl chloride to the allyldiisopropylsilanol). The cyclisation of these two materials was then performed using the standard Pauson-Khand reactions that had previously been successful in our model studies – dicobalt

• double bonds could be added catalytically to silane species to yield the substituted chlorosilanes.[33][34] This methodology was coupled with a Grignard reaction to attempt to cyclise the substituted silane (Scheme 18). The catalytic hydrosilylation using chloroplatinic acid as the catalyst proved to be

• successful yielding the desired chlorosilane with a yield of 53% which is significantly more than that stated by Swisher and Chen for the same compound. However the Grignard reaction could only be accomplished in very low yield (10%). Nevertheless, the material obtained was subjected to the P-K reaction