One-pot domino process

A number of new MCRs, that are either facilitated or accelerated by microwave irradiation, have been reported recently for the synthesis of simple N-, 0- and S-containing heterocycles. These one-pot domino processes offer... 

Selective transformations Selective styrene ring opening [103] One-pot domino process for regioselective synthesis of a-carbonyl furans [104] Tandem process for synthesis of quinoxalines [105] Atmospheric oxidation of toluene [106] Cyclohexane oxidation [107] Synthesis of imines from alcohols [108] Synthesis of 2-aminodiphenylamine [109] 9H-Fluorene oxidation [110] Dehydrogenation of ethane in the presence of C02 [111] Decomposition of methane [112] Carbon monoxide oxidation [113]... 

A novel one-pot domino process was developed to synthesize substituted 1,2-dihydroquinoline derivatives 102 with high regioselectivity using a silver catalyst <05OL2675>. Scheme 29 shows the proposed pathway, which starts with the hydroamination of alkyne 103 and aniline 104. This is followed by C-H addition with another alkyne 103 and C-H addition cyclization to give intermediate 105. The final step is another C-H addition with alkyne 103 yielding the desired product 102. The scope and mechanism of this one-pot process is still under investigation. 

Keywords Isatylidene malononitriles, a-azido ketones, ethanol, piperidine, room temperature, one-pot domino process, 3-(aminomethylene)oxindoles... 

The scope of this reaction was extended by one pot domino processes (Scheme 11). For instance, in situ hydrosilylation affords directly protected cyclohexanols 41. Saturated cyclohexanones 42 were obtained by a copper catalyzed 1,4-reduction... 

I With compound A - synthesized according to reaction (a) - the following three-component one-pot domino processes (b)/(c) in aqueous medium (as examples of Green Chemistry ) are performed ... 

In a microwave-promoted one-pot domino process, anthranihc acid (2 equiv.) was reacted with N-Boc-glycine (1 equiv.) in the presence of P(OPh)3 and pyridine at 230 °C for 20 min giving rise to a product A in 50% yield. 

Lautens and coworkers described recently a Rh/Pd-catalyzed domino synthesis of aza-dihydrodibenzoxepines (Scheme 4.28) [50]. The Rh-catalyzed hydroary-lation of 3-chloro-2-vinylpyridines 136 with 2-hydroxyphenylboronic esters 137 afforded the intermediate 138. Subsequent Pd-catalyzed C-O coupling provided the aza-dihydrodibenzoxepines 139 in good yields. The one-pot domino process worked well with electron-poor vinyl pyridines. However, the reaction did not proceed to full conversion under domino conditions with electron-rich vinyl pyridines. An asymmetric variant of this reaction was also described using both a chiral diene and an achiral phosphine as ligands, producing products in moderate to good yields with excellent enantioselectivities. This reaction represented the first example of an asymmetric multimetal-catalyzed reaction. 

Cheung, L. L. W., Yudin, A. K. (2010). Synthesis of highly substituted cyclobutane fused-iing systems from N-vinyl beta-lactams through a one-pot domino process. Chemistry - A European Journal, 16, 4100-4109. 

The one-pot multistep process has been named in various ways domino, cascade, tandem, timed, consecutive, transmissive, etc. Sometimes the word used does not describe the real meaning of the procedure in that there is no conformity between the customary use of the term and the chemical transformation. These terms were recently defined more pertinently [59]. 

Beyond the numerous applications of palladium in transition metal-catalyzed domino reactions there are a lot of other metals inducing domino processes. Ihara et al. found a strategy for the enan-tioselective synthesis of (+)-equilenin catalyzed by mangan and palladium complexes,1841 Whitby et al.1851 initiated domino cyclizations on a zirconocene template and furthermore Scherf et al. generated phenantrones by a nickel-mediated one-pot domino reaction.1861... 

A domino Diels-Alder reaction (the term was chosen from the well-known game) is a one-pot process involving two or more Diels-Alder reactions carried out under the same reaction conditions without adding additional reagents or catalyst such that the second, third, etc., cycloaddition is the consequence of the functionality generated in the previous reaction. A historical example is illustrated in Equation 1.28 [60]. This type of transformation is sometimes named tandem or cascade, but these terms seem less appropriate for describing a time-resolved transformation. 

In an anionic/radical domino process an interim single-electron transfer (SET) from the intermediate of the first anionic reaction must occur. Thus, a radical is generated which can enter into subsequent reactions. Although a SET corresponds to a formal change of the oxidation state, the transformations will be treated as typical radical reactions. To date, only a few true anionic/radical domino transformations have been reported in the literature. However, some interesting examples of related one-pot procedures have been established where formation of the radical occurs after the anionic step by addition of TEMPO or Bu3SnH. A reason for the latter approach are the problems associated with the switch between anionic and radical reaction patterns, which often do not permit the presence of a radical generator until the initial anionic reaction step is finished. 

A similar reaction (which is not a domino process in its strict definition but a useful one-pot transformation) was described by Queiroz and coworkers [116]. Reaction of bromobenzothiophene 6/1-233 with pinacolborane in the presence of Pd(OAc)2 and a phosphine followed by addition of 2-bromonitrostyrene 6/1-234 led to 6/1-235, normally in good yields (Scheme 6/1.60). 

The increasing current interest in processes that are able to generate complex molecular architectures in one pot has stimulated the development of domino-like procedures that create three bonds in one synthetic operation, with considerable advantages in terms of synthetic efficiency and environmental friendliness. This section describes some examples of the application of these concepts to the preparation of quinolizidine compounds. 

Another interesting domino Pauson-Khand reaction was presented by Cook et al. generating six carbon-carbon bonds in a one-pot process in the synthesis of dicydopenta[a,elpentalene derivatives.1801... 

As an extension of the Heck reaction, Pd-catalyzed hydroarylation of alkynes and alkenes continnes to attract high level of research interest in simple couphng processes and in cyclization reactions. The use of this type of transformation as part of a domino reaction will be of increasing interest. The research in the field of domino reactions is attracting considerable attention in synthetic organic chemistry since it enables the rapid assembly of complex molecirles in one-pot processes. Very elegant examples of palladium-catalyzed cascade processes where a single catalytic cycle entails several sequential bond transformations have been recently reported [la, b, 2a, b, c]. 

An interesting one-pot, five-component domino process using an intermolecular Diels-Alder reaction of furans with AT-phenylmaleimide as its final step has been used to construct the central core of indolo[2,3- ]carbazoles (Equation 86) <2002AGE4291>. Thus, aminooxazoles produced from an Ugi three-component reaction undergo acylation/intramolecular Diels-Alder/retro-Diels-Alder cycloreversion with pentafluorophenyl arylprop-2-ynoates to give furan derivatives. Subsequent Diels-Alder cycloaddition at elevated temperatures with A -phenylmaleimide produces carbazoles in good yields (Table 5). 

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