One-pot strategy

Enantiomers (M)- and (P)-helicenebisquinones [32] 93 have been synthesized by high pressure Diels-Alder reaction of homochiral (+)-(2-p-tolylsulfo-nyl)-l,4-benzoquinone (94) in excess with dienes 95 and 96 prepared from the common precursor 97 (Scheme 5.9). The approach is based on the tandem [4 + 2] cycloaddition/pyrolitic sulfoxide elimination as a general one-pot strategy to enantiomerically enriched polycyclic dihydroquinones. Whereas the formation of (M)-helicene is explained by the endo approach of the arylethene toward the less encumbered face of the quinone, the formation of its enantiomeric (P)-form can be the result of an unfavourable interaction between the OMe group of approaching arylethene and the sulfinyl oxygen of 94. 

Such isolated enzyme approaches for deracemization have a clear disadvantage in that they require two operational manipulations with an intermediate recovery step. A one-pot strategy is offered by employing whole-cell biotransformations with strains containing set(s) of complementary dehydrogenases operating in both biooxidative and bioreductive modes. Trace amounts of the intermediate ketone species can be isolated in several cases. In order to lead to an efficient deracemization... 

Optically active 4-substituted 1,2,4-triazoles 136a and 136b have been prepared using a simple one-pot strategy (Equation 41) <1998CRC63>. 

Recently, Nicolaou and coworkers have devised a novel, one-pot strategy for the direct transformation of acyclic olefinic esters to cyclic enol ethers [34]. Unlike the molybdenum alkylidene 1 (see Sect. 3.2), initial reaction between the Tebbe reagent 93 and an olefinic ester results in rapid carbonyl olefination to afford a diene intermediate. Subsequent heating initiates RCM to afford the desired cyclic product (Scheme 17). 

The addition of nitromethane (56% yield/168h 87% ee) or methyl a-cyanoacetate (94% yield/52h 82% ee) as alternative CH-acidic methylene compounds required increased reaction temperatures (60 to 80 °C) to furnish the adducts 7 and 8. As exemplarily depicted in Scheme 6.69 for benzylic alcohol thiourea 12 catalyzes the transformation of the obtained malononitrile Michael products to the respective carboxyhc acid derivatives (89% yield/88h). This method of derivatization also described for methanol (87% yield/24h rt), benzyl amine (77% yield/3h rt), and N,0-dimethylhydroxyamine (75% yield/20h 60°C) as nucleophiles was reported to be feasible as a one-pot strategy without isolation of the initially formed Michael adduct [222]. 

Koeller KM, Wong C-H (2000) Synthesis of complex carbohydrates and glycoconjugates enzyme-based and programmable one-pot strategies. Chem Rev 100 4465 1494... 

The alkenylation reaction of ct-halo carbonyl compounds with alkenylindium in the presence of triethylborane proceeds via a radical process. Unactivated alkene moieties as well as a styryl group can be introduced by this method. The geometry of the carbon-carbon double bonds of the alkenylindium is retained. Preparation of alkenylindium via hydroindation of 1-alkyne followed by the radical alkenylation establishes an efficient one-pot strategy (Scheme 113).384... 

Koeller KM, Wong CH. Complex carbohydrate synthesis tools for glycobiologists enzyme-based approach and programmable one-pot strategies. Glycobiology 2000 10 1157-1169. 

In the same year, Takahashi and coworkers demonstrated that various glycosyl donors could be sequenced in a one-pot strategy namely, glycosyl bromides, fluorides, or trichloroace-timidates were first coupled with a thioglycosyl acceptor (33). 

One-pot techniques combining two or more (chemo)selective glycosylation steps have been developed. One-pot strategies offer the shortest pathway to oligosaccharides, as the sequential glycosylation reactions are performed in a single flask (pot) and... 

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