The Carroll Rearrangement

These flaws were pointed out by Kimel and Cope in 1943 [4]. They observed that acetoacetates, derived from the reaction of allylic alcohols and diketene, and the benzoylacetates of several j8,y-unsaturated alcohols reacted at elevated temperatures to give y,d-unsaturated ketones and CO2 (Table 8.1). 

This mechanism seemed to make more sense compared to the mechanism proposed by Carroll for a number of reasons. Kimel and Cope suspected that the 

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The rearrangements of various allylic compounds catalyzed by both Pd(II) and Pd(0) are treated in this section[491]. Related reactions such as the Carroll rearrangement are treated in Section 2.10.1 and the Pd(II)-catalyzed Cope rearrangement is treated in Chapter 5, Section 3. 

The method of preparation of 5-dodecen-2-one presented here is a version of the literature procedure published earlier. It offers several advantages over existing methodology (1) The ester enolate modification of the Carroll rearrangement provides the allylic acetoacetates via a mild, fast, and high yield synthesis. This procedure represents a significant Improvement over... 

The Carroll Rearrangement Synthesis of 5-Dodecen-2-one S. R. Wilson and C. E. Augelli, Department of Chemistry,... 

The Carroll rearrangement, a variation on the ester Claisen rearrangement, is a useful method for the preparation of y, 8-unsaturated ketones from allyl acetoacetates, and has been adapted to provide a method for the synthesis of a number of specific arylacetones. Thus, treatment of the p-quinol 1 with diketene and a catalytic amount of DMAP at room temperature gave a 72% yield of the arylacetone 2 together with 5% of the benzofuran 3. 

Asymmetric decarboxylative rearrangement (Carroll rearrangement) of allyl a-acetamido-/3-ketocarboxylates, catalysed by a palladium complex modified with a chiral phosphine ligand, has been reported to give optically active /,5-unsaturated a-amino ketones with up to 90% ee (Scheme 92).135 The mechanism for the Carroll rearrangement is shown in Scheme 93. 

By the Carroll rearrangement, 2-methyl-2-hepten-6-one (8.34) from commercially available materials such as acetone, acetylene and ethyl acetoacetate is synthesized (Scheme 8.13). 

Among the most favorable features of the Carroll variant of the Claisen rearrangement are the relative ease of preparation of the parent system by condensation of allylic alcohols with acetoacetic estet or di-ketene and the defined configuration of the intermediately generated double bond. The Carroll rearrange-... 

An improved version of the Carroll reaction, the ester enolate Carroll rearrangement, was reported in 1984 by Wilson and Ptice. Dianions of allylic acetoacetates, generated by treatment with 2 equiv. of LDA at -78 °C in THF, were rearranged at room temperature or 65 C to yield >keto acids in 40-80% yield (equation 12). In the course of a synthesis of the sesquiterpene isocomene, Snider and Beal used this method for the rearrangement of acetoacetate (73), prepared in 83% yield from reaction of cyclopen-tene (72) with diketene and a catalytic amount of DMAP (Scheme 11). The ( )-isomer of ketone (74) is obtained stereospecifically, since there is a severe steric interaction between the methyl groups in the Carroll rearrangement transition state leading to the (Z)-isomer. 

K.L. Sorgi and co-workers prepared acetoacetates from substituted p-quinols and found that they underwent the Carroll rearrangement at room temperature to afford substituted arylacetones and related derivatives in moderate to good yields. ... 

Sorgi, K. L., Scott, L., Maryanoff, C. A. The Carroll rearrangement a facile entry into substituted arylacetones and related derivatives. Tetrahedron Lett. 1995, 36, 3597-3600. 

ZnS04, toluene, 60-80°C, 66-97% yield. This method works for allylic alcohols, which will often undergo the Carrol rearrangement followed by decarboxylation. The method can also be used to prepare esters of 3° alcohols. ... 

The rate of the Carroll rearrangement has been increased by formation of a dianion on treatment of allylic acetoacetates with two equivalents of lithium diisopropylamide in tetrahy-drofuran at — 78 CC followed by heating to reflux l0°. With one equivalent of base no reaction occurs. 

The Carroll rearrangement, first reported in 1940210-212, is an old and well-established versatile yet complementary variant of the Claisen rearrangement. The mechanism of this reaction was proposed in 1943 by Kimel and Cope213. With respect to the stereoselectivity, the most favorable feature of the Carroll rearrangement is the defined configuration of the double bond generated in the intermediate hydrogen-bonded enol. 

Besides the steric requirements of the X groups in the C-2 position of A, reaction conditions are important for the stereochemical outcome of the rearrangements. Thus, Ireland rearrangements, which can be performed under mild conditions, yield EjZ ratios >99% (see, for example, p 3324). Similarly, the Carroll rearrangement of an ester enolate proceeds smoothly (in refluxing tetrahydrofuran) to give E selectivities >90% l0°. 

The Carroll rearrangement, an old and well-established thermal rearrangement, involves the rearrangement of allyllc esters to B keto acids followed by decarboxylation to provide y,6-unsaturated methyl ketones. Even though the Carroll rearrangement fs a versatile complement to the Claisen rearrangement, It is not of widespread use. This may be due to (a) the... 

If you think these rearrangements sound like academic reactions and too refined for the rough and tumble of industry, you re in for a surprise. The Carroll rearrangement, a [3,3) sigmatropic shift, is an important industrial process used to make vitamin A and some perfumery and flavouring compounds at BASF in Germany. 

The geometry of the new double bond will be as required since the larger group prefers to be equatorial in the Carroll rearrangement transition state. 

Industrially, diketene (Chapter 33) is used in the Carroll rearrangement step and the dehydration again gives a mixture of a and j3 sinensals. 

Stephen R. Wilson and Corinne E. Augelll 210 THE CARROLL REARRANGEMENT 5-DODECEN-2-ONE... 

Scheme 3. Carbon—carbon bond formation through the Carroll rearrangement and the Tsuji-Trost reaction.

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