Subject Suzuki-type

The described fluorous-tag strategy has also been applied to the synthesis of biaryl-substituted hydantoins (Scheme 7.81) [94]. 4-Hydroxybenzaldehyde was converted into the corresponding perfluorinated species, which was then subjected to a reductive amination. The resulting amine was treated with an isocyanate to produce the fluorous-tagged urea, which spontaneously cyclized to form the corresponding hydantoin. Finally, the fluorous tag was detached by a Suzuki-type carbon-carbon bond formation to furnish the desired target structure in good yield. 

Historically, HCDC was first established for yeasts to produce single-ceU protein, ethanol, and biomass. Later, dense cultures of other mesophiles producing various types of products were developed, e.g.,by Suzuki et al. [96]. The combination of recombinant DNA technology and large-scale culture processes has enabled human proteins to be produced in a number of hosts, in particular in Escherichia coli [97-100]. Approaches to optimize the production of recombinant proteins are the subject of recent reviews from Winter et al. [101]. 

Quinazolines take part in the same types of reactions as pyrimidines, but because of their additional benzene ring, the products of these reactions may have the added feature of hindered rotation. An example of this is the synthesis of 2-phenyl-Quinazolinap by Guiry and co-workers <99TA2797>. Suzuki coupling of 4-chloro-2-phenylquinazoline (115) with boronic acids 116 led to 117 (R = OMe). These intermediates were parlayed into phosphinamines 117 (R = PPh2) and then subjected to chiral resolution to produce new chiral phosphinamine ligands for asymmetric catalysis. 

Powell, Maki, and Fu reported a Ni-catalyzed tandem radical 5-exo cyclization/ Stille coupling reaction (Fig. 19) [75]. When allylic bromo ethers 80 were subjected to a reaction with trichlorophenylstannane 81a in the presence of 10 mol% NiCl2 and 15 mol% of bipy 26, bicyclic phenyl-substituted products 82 were isolated in 57-67% yield and moderate to excellent endo-diastereoselectivity. Suzuki-Miyaura-type coupling reactions of 80 with arylboronic acids 81b worked similarly in 69-87%... 

The Suzuki coupling was developed by Professor Akira Suzuki of Hokkaido University. The Suzuki coupling uses a boron compound (R-BYj) and an alkenyl, aryl, or alkynyl halide or triflate (RX) as the carbon sources, with a palladium salt as the catalyst. Bromides and iodides are the most commonly used halides chlorides are less reactive. Alkyl halides can sometimes be used but are subject to elimination. A base is also required. The boron compound can be a borane (R jB), a borate ester (R B(OR)2), or a boric acid (R B(OH)2), where R is alkyl, alkenyl, or aryl. The general reaction is shown in the following scheme, where X is halide or triflate and Y is alkyl, alkoxyl, or OH. A list of the types of components that can be used is given in Table 24.1. This reaction is one of the principal methods now used to prepare biaryls. 

The most complex type of model is a time-dependent approach in which physical as well as chemical conditions evolve. Time-dependent methods involving both diffuse and dense clouds have been reviewed by Prasad et al. (1987) within the last year. Since no major models have appeared since the time of that review, the subject of time-dependent models will not be raised at length here. A brief history of die method is in order, however, especially as regards calculations involving dense interstellar clouds. TTie simplest approach is to allow the cloud initially under diffuse conditions to undergo a free-fall or delayed free-fall collapse concomitandy with chemical evolution. Some early treatments of this variety include those of Kiguchi et al. (1974) and Suzuki et al. (1976). 

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