Keto-compounds

Michael condensation is the addition of a compound with an active methylene group to an a, p-unsaturated keto-compound... 

It was also suggested that the relationship of the two forms (A) and (B) might be that of stereoisomerides of the cis-trans decalin type and a good deal of work was done to provide experimental evidence for this view or the alternative that they are structural isomerides. It was also found that of the methods used to synthesise the pyridocoline system all but one gave norlupinane (A) on reduetion, the exceptional formation of uorlupinane (B) being limited to reduction of the 1-keto compound by the Clemmensen method. 

When the C/D ring fusion is cis, the 17a-hydroxy compound is the main product from NaBH4 reductions of l7-keto-13a-androst-5-en-3)9-oE or 14/ -H compounds. The absence of a 10-methyl also affects the course of the reaction when rings A and B are cw-fused. A 19-nor-5/ -H 3-ketone is reduced to the 3/ -isomer, as is a 10a-H-5a-H-19-nor-3-keto compound. ... 

Reduction of a 16a-bromo-17-ketone (but not the 16 -epimer) is a little less stereospecific than reduction of the 17-keto compound. When a 2a-bromo-3-keto steroid is reduced, at least 78 % of the 3/ -alcohol is obtained. 

Axial alcohols e.g. 60) are formed predominantly when platinum is used in moderately acidic media. The use of acetic acid alone as solvent affords the equatorial alcohol as the main product from both and 7-keto compounds. Addition of 2-10% of a strong acid e.g. hydrochloric acid) to this solvent leads to the axial alcohol as the primary, if not the exclusive, product. Primary and secondary alcohols may be converted in part to the corresponding acetates under these conditions. 

This approach has been useful in obtaining C-1 oxygenated steroids and rather inaccessible 15-keto compounds. 16a-Hydroxy-A °kpi-egnanes have been obtained from the readily available 16a,17a-epoxy-20-ketones It has been shown °° that the product is a mixture of comparable amounts of the cis- and /ran -isomers (145,146), the structures of which were assigned on the basis of NMR measurements (ref. 200, see also ref. 306). 

Reaction of the 17-keto compound (54) with potassium acetylide in liquid ammonia gives the 17a-ethynylandrost-5-ene-3) ,I7)5-dioI (55). ° Similar results have been obtained with A-ring aromatic 17-ketones. ... 

In a useful modification of this method, la-methyl-A -3-keto steroids are obtained by methylation of the A -3-keto systems (20). However, it is unexpectedly difficult to convert the intermediate la-methyl-A -3-keto compound (21) into the conjugated ketone (22). 

The intermediate hydroperoxide is sufficiently stable to be isolated, and reduction with any one of a number of reagents (zinc-acetic acid is preferred) then gives the 17a-hydroxy-20-keto compound. 

If A -20-keto steroids are used as substrates, only low yields of A -17a-hydroxy-20-keto compounds are obtained. If a methyl group is also present on the double bond at C-16, the final product is a 16-methylene-17a-hydroxy-20-keto steroid. " ... 

Similar sulfenylation reactions of the 2-subsdtuted cyclic enamines of -keto carboxylic acid anilides are also possible, The trifluoromethanesulfenyl substitution takes place according to ring size Sulfenylation occurs at positions 2 and 5 with five-membered rings, at posibon 6 with six-membered tings, and at position 7 with seven-membered rings [5J (equation 4) (Table 1). Acid hydrolysis of the enamines proceeds readily to form the corresponding keto compounds. 

X0 to hydroxy compounds. Lower temperatures favor ketone formation and sterically hindered carbonyls, such as 2-thienyl t-butyl ketone, are not reduced. The sensitivity of desulfurization to steric factors is evident by the failure to desulfurize 2,5-di-i-butyl-3-acetylthiophene. The carbonyl groups of both aldehydes and ketones can be protected by acetal formation, as particularly cyclic acetals are stable during desulfurization in methanol at room temperature. " The free aldehydes give primary alcohols on desulfurization. Another method to obtain only keto compounds is to oxidize the mixtures of ketone and secondary alcohol with CrOs after the desulfurization. - Through the desulfurization of 5,5 -diacetyl-2,2, 5, 2"-terthienyl (228), 2,15-hexadecandione (229) has been obtained, which... 

Cytochrome PTSOiy, carries out comparable reactions for removal of the side chain of pregnenolone, and two reactions have been described both of which involved loss of acetate—17a-hydroxylation and formation of the 17-keto compound, and direct formation of the A -ene (Figure 3.19c) (Akhtar et al. 1994). 

The Crignard reactant having a long alkyl chain was added to a keto compound the substituents remain undisclosed [134]. Thereby, an enolate is formed which is further reacted in the framework of a multi-stage fine-chemical industrial process. 

Drivers for Performing Chlorination of a-Keto Compounds in Micro Reactors... 

Beneficial Micro Reactor Properties for Chlorination of of a-Keto Compounds... 

Chlorination of of a-Keto Compounds Investigated in Micro Reactors Cas/liquid reaction 14 [CL 14] Chlorination of acetic acid... 

There are two important rhodium-catalyzed transformations that are broadly used in domino processes as the primary step. The first route is the formation of keto carbenoids by treatment of diazo keto compounds with Rh11 salts. This is then followed by the generation of a 1,3-dipole by an intramolecular cyclization of the keto carbenoid onto an oxygen atom of a neighboring keto group and an inter- or intramolecular 1,3-dipolar cycloaddition. A noteworthy point here is that the insertion can also take place onto carbonyl groups of aldehydes, esters, and amides. Moreover, cycloadditions of Rh-carbenes and ring chain isomerizations will also be discussed in this section. 

Treatment of A 8(9)-dehydroestradiol with trifhioroacetic acid and triethylsilane gives estradiol in 96% yield (Eq. 86).239 The 3-methyl ether is similarly reduced to the 3-methyl ether of estradiol in >50% yield.239 The structurally related 18-ethyl and 18-propyl 17-keto compounds experience reduction of the A8(9) function in excess of 70% yield without concomitant reduction of the 17-keto... 

Synthesis of the pyridine derivative, in which the nitrogen is closest to the A-ring was also described by Simoni et al. [60], is shown in Scheme 34 and was more productive than the synthesis described in Scheme 33. The keto-compound 134 was reacted with the vinamidinium hexafluorophosphate salt (CDT-phosphate) 135, ferf-BuOK, ammonium acetate, and an equimolar amount ofDABCO (l,4diazabicyclo[2.2.2]octane). Hydrogenation using 10%... 

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