Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• ′-bromobiphenyl intermediates necessary for the preparation of 4a–c were synthesized by the Suzuki–Miyaura cross-coupling of 1-bromo-4-iodobenzene with the corresponding boronic acids/esters 1a–c in the yields of 82, 84, and 91%, respectively. A routine procedure involving a lithiation and reaction with

• % yield). Since the Sonogashira reaction between bromo derivatives and trimethylsilylacetylene proved to be sluggish and low yielding (even with a large excess of acetylene and elevated temperature), the bromo derivatives were converted to the corresponding iodo derivatives by lithiation and quenched with

• . Overall 12 extended π-linkers have been easily synthesized (8 of them are new compounds) utilizing procedures such as a lithiation/reaction with triisopropyl borate/esterification with pinacol, Mizoroki–Heck coupling with vinylboronate pinacol ester, borylation with bis(pinacolato)diboron or Sonogashira

Enantiospecific synthesis of [2.2]paracyclophane- 4-thiol and derivatives

• Gareth J. Rowlands and
• Richard J. Seacome

Beilstein J. Org. Chem. 2009, 5, No. 9, doi:10.3762/bjoc.5.9

• by sulfinyl-directed ortho lithiation with n-butyllithium followed by reaction with tosyl azide. The resulting azo[2.2]paracyclophane was reduced in situ to give the amine (Rp,RS)-8 in good yield for the two steps (Scheme 2). Trichlorosilane-mediated deoxygenation proceeded uneventfully to furnished

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• potassium tert-butoxide (KOR) in tetrahydrofuran at −100 °C. Upon trapping with molecular iodine, 3-iodo-4-trifluoromethoxybiphenyl was isolated in 90% yield [73]. Under the same conditions as employed with trifluoromethoxybenzene, 1- and 2-trifluoromethoxynaphthalene undergo selective lithiation at the 2

• lithiation next to the OCF3 substituent is favoured, probably due to steric reasons. In fact, 1-trifluoromethoxy-4-(trifluoromethyl)benzene (Scheme 15) affords 2-trifluoromethoxy-5-(trifluoromethyl)benzoic acid after lithiation and carboxylation [75]. When the OCF3 substituent is in competition with fluorine

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

• -thiophenecarbonyl chloride 2 was developed from tetrachlorothiophene via either a lithiation reaction with n-butyllithium in MTBE solvent, or by a previously reported Grignard method using 1,2-dibromoethane as activator, followed by carbonation of the anion with CO2 to give the trichloro-2-thiophenecarboxylic acid

• with CO2, 3,4,5-trichloro-2-thiophenecarboxylic acid 23 was isolated and dried prior to its conversion to 2 with thionyl chloride. Thus, 2 can be prepared in two chemical steps from the inexpensive chlorinated thiophene 22 using either lithiation or Grignard chemistry. [28] A comparison of some key

• manufacturing issues surrounding the two proposed routes to 2 via 23 is summarized in Table 2. The two routes are dramatically different and lead to significantly different yields. At first glance, the lithiation route is clearly superior due to the 92% isolated yield, and the formation of only one equivalent