Cyclopropanone cyanohydrins

Explored initially by Reich,cyanide addition to acyl silanes can produce Brook rearrangement, leading to an additional cascade of steps in appropriately designed systems. For example, Takeda, using a crown ether as a phase transfer agent but under non-aqueous conditions, showed that cyanide addition to acyl silanes and subsequent Brook rearrangement led, in the case of y bromo acyl silane 59 to intramolecular alkylation and formation of cyclopropanone cyanohydrin derivative 60. ... 

The protected cyclopropanone cyanohydrin (15) has been converted into cyclobutanone, which can also be obtained by an identical route from 4-chlorobutanal. Tricyclo[3,2,0,0 ]heptan-6-ones have beat implicated as reaction intermediates in... 

A noteworthy example of an unexpected result in this area is the cyanation of l-chloro-3-phenyl-propan-2-one (15) with sodium or potassium cyanide in aqueous acetone which yielded the condensation product 16 in 55% yield.It is proposed that the reaction occurs via a Favorskii-type 1,3-dehydrochlorination, followed by trapping of the intermediate cyclopropanone 18 by cyanide to give cyanohydrin 19, which is not isolable. Instead, it adds across the intermediate cyclopropanone 18 to give adduct 20, which opens in the so-called normal way to afford the most stable carbanion 21, the benzylic carbanion. On protonation, the final cyclopropanecar-bonitrile 16 is formed and isolated as one stereoisomer, resulting from stereospecific addition of cyanide to the intermediate cyclopropanone. As expected, the isomeric 1-chloro-l-phenyl-propan-2-one (17) reacted in similar manner with aqueous cyanide to afford adduct 16, albeit in a lower yield. 

Cyclopropanone and cyclobutanone cyanohydrins. Stork has extended his synthesis of ketones from protected cyanohydrins of aldehydes (equation I) to a synthesis of cyclic ketones, in particular, cyclopropanone and cyclobu-... 

It should be mentioned that perfluoro- and perchlorocyclobutanones form stable a-halohydrins (10) in the same manner that chloral and a-ketoalde-hydes do. Cyclopropanones (11) give hydrates, hemiacetals, and cyanohydrins extremely readily. 

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