1,3-Dicarbonyl compounds cascades

Kaupp G, Naimi-Jamal MT. Quantitative cascade condensations between o-phenylene-diamines and 1,2-dicarbonyl compounds without production of wastes. Eur J Org Chem 2002 1368-73. 

Following a similar reaction design, a cascade Michael/aldol reaction has been studied using other different 1,3-dicarbonyl compounds for the building up of highly functionalized cyclohexanes containing multiple stereogenic... 

The Studer group presented a new cascade for the highly enantioselec-tive synthesis of substituted indane derivatives. Three stereocenters are formed in the NHC-catalyzed cascade reaction of enals with various p-dike-tones to give the corresponding indane derivatives with excellent stereoselectivity (up to 74% yield, 99% ee). It is predicted that the reaction occurs via a catalytic cycle using oxidative NHC catalysis. Reaction of the enal with NHC in the presence of an oxidant generates an o,p-unsaturated acylazolium ion. Conjugate addition of the likely deprotonated 1,3-dicarbonyl compound... 

The organocatalyzed cascade reaction of 1,3-dicarbonyl compounds with Morita-Baylis-HiUman acetates of nitroalkenes give access to benzo ]chro-man-type derivatives in good-to-exceUent yields and with high diastereo- and... 

Xu and Dixon and co-workers also described a trimolecular cascade process, also involving a nitro-olefln. In this case, however, the nucleophile was a 1,3-dicarbonyl compound 183 whose 1,4-addition into the nitro-olefln 185 was facilitated by bifunctional thiourea catalyst 186. However, a secondary amine... 

Pyrrole 38 was generated from nitrobenzene and a 1,4-diketone with indium metal in acetic acid. The reductive conditions convert nitrobenzene to aniline in situ cyclization then occurs with the dione in moderate to excellent yield (40-98%, 21 examples) (13T6698). A Pd(OCOCF3)2-catalyzed cascade furnished tetrasubstituted pyrrole 39 from 1,3-dicarbonyl compounds and primary amines in good yield (13CC4667). 

So far, we have demonstrated that the carbonyl functionality of aldoses can successfully be used in several cascade reactions (aldehyde in the acyclic structure). Also, ketoses proved to be useful substrates in cascade reactions with 1,3-dicarbonyl compounds (ketone in the acyclic structure). In these reactions, several unusual and highly substituted carbohydrates were formed with high degrees of chemoselectivity as well as stereoselectivity. 

AMINE-CATALYZED CASCADE REACTIONS OF KETOSES WITH 1,3-DICARBONYL COMPOUNDS... 

Similar to the mechanism described in Scheme 2.16, a Knoevenagel reac-tion/ketalization cascade of hydroxyacetone with 1,3-dicarbonyl compounds is assumed. In Scheme 2.16, a Knoevenagel condensation/ketalization reaction is depicted. This sequence allows a subsequent oxa-Michael addition, which yields the corresponding C-glycosides. In contrast, a Knoevenagel addition/ketalization occurs under the reaction condition described in Scheme 2.28, which is followed by an intramolecular retro-Claisen step. As a result of that, the corresponding esters were obtained (Scheme 2.29). 

SCHEME 2.29 Amine-catalyzed cascade reactions of hydroxyacetone with 1,3-dicarbonyl compounds. 

Cascade reactions of benzodioxaphosphepine (17) with a-dicarbonyl compounds such as 9,10-phenantrenequinone (18) and dibenzoyl (19) gave other cage-like propeller derivatives (20) and (21) with five- and seven membered rings containing phosphorus-carbon bonds. They were also reported to be hydrolytically unstable (Scheme 4). ... 

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