One-pot synthetic approach

Hyperbranched polymers are synthesized in a one-step method, often from AB monomers but also by combining A +B (x>3) monomers or variations of those. Polymerization methods have been applied that involve polycondensation, polyaddition, and ring-opening or self-condensing vinyl polymerization. Even though the one-pot synthetic approach leads to imperfectly branched structures because of uncontrolled growth, it is more suitable for the preparation on a larger scale and thus for commercial use. Nowadays, different... 

Wang and co-workers have recently reported a generalized strategy for the synthesis of a variety of ternary metal sulfides with controlled size, morphology, (Fig. 25) crystallographic phase and stoichiometric composition. This one pot synthetic approach is primarily based on co-thermal decomposition of diethyldithiocarbamate complexes of corresponding metals in oleylamine and dodecanethiol surfactants. 

Rather than using a metal-catalyzed synthesis of the requisite aminoalkyne substrate, Dixon and coworkers used a one-pot synthetic approach beginning with a base-catalyzed nitro-Mannich reaction for the assembly of this reactive intermediate (Scheme 15.101). Sequential addition of the AuClj catalyst for the pyrrole ring formation then afforded the N-protected 2,5-substituted products in good yields (typically 56-76% overall yield from the imine starting material) [328]. 

Recently, Heydari and coworkers have employed dehy-droascorbic acid capped magnetite (DHAA-FejO ) catalyst for the one-pot synthetic approach of synthesis of a-aminonitriles. Final adducts are obtained with high yields employing different aldehydes or ketones and amines. A plausible... 

The librariesPPl of U-4CR products already mentioned in 1961,were not prepared until 1995. Since then, this approach has found widespread application in industrial chemical research. It is expected that this one-pot, multicomponent approach will play an essential role in synthetic organic strategies in the future.P 1... 

Metzner and co-workers reported a one-pot epoxidation reaction in which a chiral sulfide, an allyl halide, and an aromatic aldehyde were allowed to react to give a trons-vinylepoxide (Scheme 9.16c) [77]. This is an efficient approach, as the sulfonium salt is formed in situ and deprotonated to afford the corresponding ylide, and then reacts with the aldehyde. The sulfide was still required in stoichiometric amounts, however, as the catalytic process was too slow for synthetic purposes. The yields were good and the transxis ratios were high when Ri H, but the enantioselectivities were lower than with the sulfur ylides discussed above. 

Several syntheses of annulated uracils of biological value were recently reported. The key reaction was a microwave-assisted one-pot [4 -i- 2] cycloaddition of oxazino[4,5-d]-, pyrano-[2,3-d]-, pyrido[2,3-dj- and pyrimido[4,5-djpyrimidines, in the sohd state [134] and under solvent-free conditions [135]. The synthetic approach was based on the reaction of NJ -di-methyl-5-formylbarbituric acid 208 with maleimide in the sohd state for 5 min under microwave irradiation at 120 °C to give the pyrano[2,3-d]pyrimi-dine derivative 209 in 90% yield (Scheme 76). The reaction of 208 with phenyl isocyanate under microwave irradiation in the absence of solvent... 

An alternative approach was achieved by the one-pot reaction of dichlo-rosilane with RPH2 in the presence of two equivalents of nBuLi. However, neither synthetic method yields crystalline phosphasilenes. The first synthesis of the crystalline phosphasilene 13 was achieved by a two-step reaction of fBuSiCl3 with 4 equivalents of RPHLi (R = 2,4,6-/Bu3C6H2) and Ph2PCl by Niecke et al. in 1993 (Scheme 3).10c This reaction proceeds... 

A classical approach to driving the unfavorable equilibrium of an enzymatic process is to couple it to another, irreversible enzymatic process. Griengl and coworkers have applied this concept to asymmetric synthesis of 1,2-amino alcohols with a threonine aldolase [24] (Figure 6.7). While the equilibrium in threonine aldolase reactions typically does not favor the synthetic direction, and the bond formation leads to nearly equal amounts of two diastereomers, coupling the aldolase reaction with a selective tyrosine decarboxylase leads to irreversible formation of aryl amino alcohols in reasonable enantiomeric excess via a dynamic kinetic asymmetric transformation. A one-pot, two-enzyme asymmetric synthesis of amino alcohols, including noradrenaline and octopamine, from readily available starting materials was developed [25]. 

All synthetic references are printed in boldface in Tables 1-3. The synthetic methods reported have been classified below into several general approaches according to a one-pot construction of one, two, and three fused heterocyclic ring systems. 

A synthetic route for the convenient preparation of the 4-substituted-3-iodofurazans 150 has been developed. The approach is accomplished by one-pot diazotization-iodination reaction of the corresponding aminofurazans 149 (Equation 25) <2004HAC199>. 

Somei and co-workers made extensive use of the Heck reaction with haloindoles in their synthetic approaches to ergot and other alkaloids [26, 40, 41, 240-249]. Thus, 4-bromo-l-carbomethoxyindole (69%) [26], 7-iodoindole (91%) (but not 7-iodoindoline or l-acetyl-7-iodoindoline) [40, 41], and l-acetyl-5-iodoindoline (96%) [41] underwent coupling with methyl acrylate under standard conditions (PdlOAc /PhsP/EtjN/DMF/100 °C) to give the corresponding (E)-indolylacrylates in the yields indicated. The Heck coupling of methyl acrylate with thallated indoles and indolines is productive in some cases [41, 241, 246]. For example, reaction of (3-formylindol-4-yl)thallium bis-trifluoroacetate (186) affords acrylate 219 in excellent yield [241], Similarly, this one-pot thallation-palladation operation from 3-formylindole and methyl vinyl ketone was used to synthesize 4-(3-formylindol-4-yl)-3-buten-2-one (86% yield). 

The application of this synthetic approach to bromodialkenyl amines 251 results in a novel one-pot synthesis of tetrahydroisoindolines 252 (Scheme 72) [124]. 

---