Rearrangement acyloins

The oxygen derivative 39a has its origins in the acyloin reduction product of diethyl succinate 45. A benzylic acid type of rearrangement of in situ formed... 

The 1,2-shift of pcrfluoroalkyl groups from carbon to carbon has been reported in an acyloin-like rearrangement of 4-hydroxy-4-(perfluorooctyl)cyclohexa-2,5-dien-l-one (19) to hy-droquinone 20.13... 

Keywords 17a-hydroxy-20-ketosteroid, acyloin rearrangement, substitutive rearrangement, stereoselective, gas-solid reaction... 

A-acyliminium ions (equations 41, 43, 55 and 56) Danilov rearrangement of aldehydes 347 into ketones 349149 (equation 95), the acyloin rearrangement 350 -> 35290 (equation 96) and dienone-phenol rearrangement 353-355150 (equation 97). 

A skeletal rearrangement of a-hydroxyketones (103), similar to the known acid-catalysed acyloin transformation (Favorski, 1926), has been observed by Frearson and Brown (1968), who made efforts to distinguish between the possibilities of rearrangements taking place before and after ionization. These workers were of the opinion that an ion-rearrangement had been observed but the interpretation is open to question. 

Acyloins. The anion of the adduct of cyanotrimethylsilane with benzaldehyde reacts with aldehydes and ketones to form acyloin silyl ethers (2), by way of a 1,4-O-siIyI rearrangement, a—>b. On hydrolysis acyloins (3) are obtained in high yield. 

Several examples are known of the contraction of steroid rings by benzilic acid rearrangements of a -diketones [2g2]. Acyloin rearrangements in the steroid field, particularly in the conversion of i7-hydroxypregnan-20 ones into D-homo-ketols,... 

A reaction similar in character to the base-catalysed acyloin rearrangement occurred when the i7a-hydroxy-20-ketone was heated in liquid ammonia [216]. The product, a i i mixture of i7a-epimeric amino-17-ketones (7) and (8) is best explained... 

The two general methods for preparation of 4-imidazoline-2-thiones are the reaction of acyloins with thioureas and the acid hydrolysis of alkyl- or arylthiureidoacetals. The above reactions have been summarized in a review by Hofmann. Aren and Bite recently reported that the 2-phenyl-2-thiureido-l,3-indanediones (17) undergo rearrangement in strong acid to produce in high yield a series of 4-imidazoline-2-thiones (18). 

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