Addition rearrangements with

Carboxylic acids react with butadiene as alkali metal carboxylates. A mixture of isomeric 1- and 3-acetoxyoctadienes (39 and 40) is formed by the reaction of acetic acid[13]. The reaction is very slow in acetic acid alone. It is accelerated by forming acetate by the addition of a base[40]. Addition of an equal amount of triethylamine achieved complete conversion at 80 C after 2 h. AcONa or AcOK also can be used as a base. Trimethylolpropane phosphite (TMPP) completely eliminates the formation of 1,3,7-octatriene, and the acetoxyocta-dienes 39 and 40 are obtained in 81% and 9% yields by using N.N.N M -tetramethyl-l,3-diaminobutane at 50 in a 2 h reaction. These two isomers undergo Pd-catalyzed allylic rearrangement with each other. 

Addition reactions with tetracyanoethane have provided access to 2,5-diamino-3,4-dicyano-thiophene and -selenophene (58JA2775,81ZOR1958). Base catalyzed rearrangement gives the isomeric pyrrolethiol (Scheme 53). 

The initial series of major tranquilizers consists of alkylated derivatives of 4-aryl-4-hydroxypiperidines. Construction of this ring system is accomplished by a set of rather unusual reactions. Condensation of methylstyrenes with formaldehyde and ammonium chloride afford the corresponding hexahydro-1,3-oxazines (119). Heating these oxazines in the presence of acid leads to rearrangement with loss of water to the tetrahydropyridines. Scheme 1 shows a possible reaction pathway for these transformations. Addition of hydrogen bromide affords the expected 4-bromo compound (121). This last is easily displaced by water to lead to the desired alcohol (122) The side chain (123) is obtained by Friedel-Crafts acylation of p-fluorobenzene with 4-chloro-butyryl chloride. Alkylation of the appropriate arylpiperidinol with 123 affords the desired butyrophenone derivative. Thus,... 

Quite recently, Wipf and coworkers developed a combination of a Claisen rearrangement with the addition of an organo aluminum species to the newly formed carbonyl moiety [108]. The new process is based on an already-discussed (see above) transformation by the same author [104]. 

A new domino lithium acetylide addition/rearrangement procedure on trans-1,2-dibenzoyl-3,5-cyclohexadiene furnished 3-alkylidene-2,3-dihydrofurans via an intriguing mechanism involving three bond formations and two bond cleavages in one single operation <06SL1230>. The reaction of dimedone with meso-diacetoxycyclohexene in the presence of a palladium catalyst led to the formation of the tricyclic product as depicted below <06S865>. 

These electrophilic conjunctive reagents require donor reactants. The cyclopropyl-carbinols as precursors to cyclobutanones arise by simple addition of organometallics. For example, the cyclobutanone 47 derives by addition of vinyllithium to 44 followed by rearrangement with aqueous fluoroboric acid 92). In some cases, this route to cyclopropylcarbinols is preferred. Addition of 41 to aldehydes or ketones... 

The preparation of conjugated diene complexes will be presented by groups. In addition, isomerization reactions, or degenerate rearrangements with activation energies >25 kcalmol-1, will be considered in this section. 

However, in an intriguing reaction promoted by the para-nitro groups of the aryl-sulphone (1) (Scheme 6.25), the initial Michael adduct derived from acrylic esters produces the diarylpropanoic esters (2), together with the diesters (3) (from methyl or ethyl acrylate) [39]. A similar addition-rearrangement reaction has been observed with l-aryl-2-(4-nitrobenzenesulphonyl)ethanones [40]. Additionally, reaction of the sulphonylethanone with two equivalents of the acrylic ester produces a 4-hydroxy-1,4-diarylcyclohexane-1,3-dicarboxylate. 

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