Carbonylative synthetic transformation

Still another synthetic route to gibberellic acid has been developed which differs from those above in the transforms used to disconnect the various rings, but which also depends on the initial disconnection of ring A (using aldol and carbonyl addition transforms). ... 

The required nitrite esters 1 can easily be obtained by reaction of an appropriate alcohol with nitrosyl chloride (NOCl). The 3-nitroso alcohols 2 formed by the Barton reaction are useful intermediates for further synthetic transformations, and might for example be converted into carbonyl compounds or amines. The most important application for the Barton reaction is its use for the transformation of a non-activated C-H group into a functional group. This has for example been applied for the functionalisation of the non-activated methyl groups C-18 and C-19 in the synthesis of certain steroids. ... 

The mechanistic aspects of nucleophilic substitutions at saturated carbon and carbonyl centers were considered in Part A, Chapters 4 and 7, respectively. In this chapter we discuss some of the important synthetic transformations that involve these types of... 

Hydrogenation of the carbonyl function is an important synthetic transformation and can be catalyzed by complexes of several transition metals including -among others- Co, Rh, Ru, Ir, and Os. In aqueous organometallic catalysis the first examples were given by the hydrogenation of water-soluble 2-oxo-carboxylic acids, 1,3-dihydroxyacetone and fmctose [47-54], later the same substrates were also used for testing new catalysts [29]. 

A promising synthetic transformation is the reaction of carbenoid intermediates with heteroatoms to form ylides that are capable of undergoing further transformations [5,6]. Enantioselective transformations in which the ylide intermediates undergo either 1,2- or 2,3-sigmatropic rearrangement were briefly reviewed in the previous issue (Vol. II, pp. 531-532) and several recent examples have appeared [37]. A major breakthrough has been made in the enantioselective transformation of carbonyl ylides derived from capture of the metal carbenoid intermediates by carbonyl groups. The carbonyl ylides have been ex-... 

Abstract Ruthenium-catalyzed carbonylation reactions are described. The purpose of this chapter is to show how ruthenium complexes as catalysts are important in the recent development of carbonylation reactions. This review does not present a complete, historical coverage of ruthenium-catalyzed carbonylation reactions,but presents the most significant developments of the last 10 years. The emphasis is on novel and synthetic transformations of genuine value to organic chemists. Especially, this review will focus on carbonylative cycloadditions and carbonylation of C-H bonds. The review is generally organized according to the nature of the reaction. 

Reduction of acid chlorides to aldehydes One of the most useful synthetic transformations in organic synthesis is the conversion of an acid chloride to the corresponding aldehyde without over-reduction to the alcohol. Until recently, this type of selective reduction was difficult to accomplish and was most frequently effected by catalytic hydrogenation (the Rosenmund reduction section 6.4.1). However, in the past few years, several novel reducing agents have been developed to accomplish the desired transformation. Among the reagents that are available for the partial reduction of acyl chlorides to aldehydes are bis(triphenylphosphine)cuprous borohydride , sodium or lithium tri-terf-butoxyaluminium hydride, complex copper cyanotrihydridoborate salts °, anionic iron carbonyl complexes and tri-n-butyltin hydride in the presence of tetrakis(triphenylphosphine)palladium(0). ... 

In some cases, there appears to be competition between reaction of (3) with the carbonyl and with the terminal alkene product. In the latter case a metallacycle is believed to be formed, which, on protonolysis, leads to the product of em-dimethylation of the original carbonyl. This transformation has only been observed with unhindered aldehydes and ketones, but does, in itself, provide a rather useful synthetic sequence (equation 23). 

Over the last 20 years, the applications of sulfones in synthetic organic chemistry have dramatically increased.3,4 The carbonyl group is often desired in the target organic molecule, but the sulfonyl group is almost always removed, so that the sulfone functions as a versatile tool in such synthetic transformations. 

The authors have designed modified bis(organoaluminum) reagent 49 for the efficient simultaneous coordination toward carbonyls (type E2), and successfully elucidated its reactivity and selectivity in the typical synthetic transformations [58J. 

Note, for many synthetic transformations, it is convenient to ntiUse halo- or alkoxy-diazines, in lien of the (oxidation level) equivalent carbonyl compounds. Often this device facilitates solnbiUty a final hydrolysis converts to the carbonyl form. 

Finally, a solid phase version of the Reissert reaction has been developed for combinatorial chemistry purposes, and differently substituted isoquinolines have been prepared (Figure 15.16). Starting from polymer-supported benzoyl chloride, isoquinoline was bound and treatment with trimethylsilyl cyanide (TMSCN), followed by alkylation, yielded resin 31. After performing synthetic transformations (carbonylation etc.), Reissert hydrolysis was induced with aqueous NaOH in THF. 

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