Coupling precursor

Another milestone synthesis was reported by the group of Kende the same year as the Schlessinger and the Raphael syntheses, Fig. (20) [120], The synthetic sequence arrived at the same keto-acid intermediate 89 as in the Raphael synthesis. The oxidative coupling precursor 90 was obtained... 

Side Product Precursor Coupled Precursor Impurity... 

Attachment of 1,5-pentanediol to a Merrifield resin (benzylic chloride) under basic conditions (NaH, DMF, 80 °C) followed by conversion to the bromide and then esterification with />-iodobenzoic acid leads to coupling precursor Many... 

Many chemical reaction schemes have been proposed and they can be classified as follows direct oxidation of benzene, organometallic coupling, precursor methods, and electrochemical syntheses [135,158,216-224]. 

Manipulation of our phenol protecting groups accessed our desired coupling precursors. Methylation of the free phenol followed by EOM (ethox-ymethyl) deprotection allowed access to our coupling precursors 38. While acid deprotection worked well with the pigmentosin A and talaroderxines monomers, the TIPS and TBDPS groups would not survive the harsh acidic conditions. Heating the TIPS-protected naphthopyranone in neat... 

Show the structural relationship between the following natural products and oxidative phenolic coupling precursors. (Morphine-5)... 

In 2004, Harayama and coworkers reported an intramolecular C-H arylation between two heteroarenes (Scheme 16.30) [65]. The coupling precursor 146, which was synthesized by Ai-alkylation of 4-quinazolinone with 2-bromo-3-(bromomethyl)quinoline, was cyclized using catalytic Pd(OAc)2 and PPhj to give luotonin A in 66% yield. This natural product was then hydroxylated in two steps to provide luotonin B as well as rutaecarpine using the same strategy. 

The scope of the Suzuki cross-coupling reaction has been further increased by the utilization of novel boron derivatives. The synthesis of these coupling precursors has also been simplified as they are accessible from aromatic halides by means of a palladium-catalyzed procedure, which is more tolerant to functional groups than the original lithia-tion protocol. Examples of aromatic boron species are shown in Figure 12.3. A detailed account on boron species employed in Suzuki couplings has recently been published [120],... 

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