Additive- and vinylogous

Additive and Vinylogous Additive Pummerer Reactions Sila-Pummerer Reactions Preparation ofTrimethylsiloxy Sulfides The Abnormal Pummerer Reaction... 

Padwa, A., Kuethe, J. T. Additive and Vinylogous Pummerer Reactions of Amido Sulfoxides and Their Use in the Preparation of Nitrogen Containing Heterocycles. J. Org. Chem. 1998, 63, 4256-4268. 

The carbanion -type reactivity of dienamine activation can be promoted by a silyl-protected diarylprolinol catalyst in the presence of reactive electrophilic species, such as nitroolefins or diarylmethanols (Scheme 2.10) [20]. Although both direct addition (a-addition) and vinylogous addition (y-addition) are viable reaction pathways, the a-reactivity is the more typical one and usually provides better selectivities due to more effective shielding of the a-position by the aminocatalyst. Interestingly, the a-/y-selectivity of dienamine-mediated carbanion -type addition reactions seems to be strongly influenced by the substitution pattern of the enal reactant For example, it was demonstrated that y,y-disubstituted enals favor the a-addition product while y-functionaUzation is the predominant reaction pathway for y-monosubstituted enals. 

The Michael reaction is of central importance here. This reaction is a vinylogous aldol addition, and most facts, which have been discussed in section 1.10, also apply here the reaction is catalyzed by acids and by bases, and it may be made regioselective by the choice of appropriate enol derivatives. Stereoselectivity is also observed in reactions with cyclic educts. An important difference to the aldol addition is, that the Michael addition is usually less prone to sterical hindrance. This is evidenced by the two examples given below, in which cyclic 1,3-diketones add to o, -unsaturated carbonyl compounds (K. Hiroi, 1975 H, Smith, 1964). 

Steps Including (TiCI2(0-/-P r)a) catalyzed vinylogous aldol addition and hydroxy directed reduction of C3 ketone using Me4NB(OAc)3H... 

A quantitative solid-state ene addition between two ligands of the platinum complex 397 gives the rearranged platinum complex 398 upon extensive heating to 140 °C [123]. This rearrangement reaction (cf. Sect. 24) is treated here, as it is the only known quantitative solid-state ene addition to date. Further quantitative solid-state [4-1-4] additions and higher vinylogs, as well as ene additions also of the intermolecular type, await detection both as thermal and photochemical reactions. 

Malonate esters and vinylogous malonates, as well as 1,3-diketones, readily undergo diazo transfer. In addition, the less acidic -keto phosphonates (138 equation 55) ° and p-keto sulfones (140 equation 56) have been shown to participate in this reaction. 

In the laboratory of S.F. Martin, a biomimetic approach toward the total synthesis of ( )-strychnine was developed by using tandem vinylogous Mannich addition and HDA reaction to construct the pentacyclic heteroyohimboid core of the natural product.The commercially available 4,9-dihydro-3/-/-P-carboline was first converted to the corresponding A/-acylium ion and then reacted with 1-trimethylsilyloxybutadiene in a vinyiogous Mannich reaction. The resulting cycloaddition precursor readily underwent the expected HDA reaction in 85% yield. 

Atom Variations E2 Heteroatom Variants, Dehalogenation, Fragmentation Vinylogous Variations Sn2 and E2. 1,4 additions Extent of Proton Transfer Variations General Acid and General Base Catalysis of Additions and Eliminations, Summary by Media, Push-Pull Catalysis of Enolization... 

Scheme 10.22 Vinylogous Michael addition and domino Michael-retro-Michael reaction.

The attack of the acid (154) on the readily polarizable 1,2-dithiafulvene (155) corresponds to the extremely ready addition of electrophilic reagents to the simple and vinylogous heptafulvene derivatives, which are iso-n-electronic with 155. The opening of the dithiole rings in 156 and 158 under the pressure of the carbanionoid electron pair liberated by the proton abstraction and of the free electron pair on the sulfur, as well as the elimination of elementary sulfur and the intramolecular electrophilic attack of the mercaptide ion (157) on the 5-position to form 158, are simply the typical reactions of 1,2-dithioles that have already been discussed (Section II, B, 3). The reactivity of the 3-methyl group in 154 finds many parallels in the ease of condensation of the methyl-substituted pyridinium, pyrylium, thiopyrylium, and tropylium salts, and particularly... 

Biphenyl and alicyclic derivatives. Phosphoric acids (117) catalyzed addition of j8-diketones, jS-ketoesters, and vinylogous amides to a,j8-unsaturated aldehydes to give substituted chromenones, pyranones, and tetrahydroquinolinones in good yields, under mild reaction conditions, via a formal [3 -h 3] cycloaddition (Scheme 28). ... 

Huang [80] and Liu [81] independently described a copper-catalyzed indole synthesis involving 2-iodoaniline and allenes (e.g., ethyl buta-2,3-dienoate) in a process that involved in situ formation of an aza-Michael addition adduct (vinylogous carbamate) and intramolecular Hecklike cyclization. Both groups used similar reaction... 

Reviews cover organocatalytic vinylogous reactions (both direct and Mukaiyama), recent contributions to regio-, enantio-, and diastereo-control in vinylogous aldol additions, and a 10-year survey of progress in the area (369... 

An interesting case of aldol condensation is vinylogous aldol reaction. The y-hydrogen of a,P-unsuturated ketones, nitriles and esters is active and the electrophilic addition taken place at the y-position. Thus, the reaction of isophorone with benzaldehyde in water gives only vinylogous aldol addition but with low conversion. However, in presence of CTACI, the condensation product, (E)-benzylideneisophorone, is obtained in 80% yield. Use of tetrabutylammonium chloride (TBACl) gives a mixture of addition and condensation products (Scheme 36). ... 

A review, see X. Jusseau, L. Chabaud, C. Guillou, Synthesis of y-butenolides and a, 3-unsaturated y-butyrolactams by addition of vinylogous nucleophiles to Michael acceptors. Tetrahedron 70 (2014) 2595-2615. 

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