Synthesis from carbonyl compounds

This reaction was used as the basis for the development of a procedure for the synthesis of carbonyl compounds (182) from acetophenone derivatives (180) (386) (Scheme 3.138). 

The resulting radicals R efficiently alkylate BENAs (495) at the (3-C atom to give silyl derivatives of oximes (496) in good yields. The latter readily undergo deoximation in the presence of 1 M hydrochloric acid to give the corresponding carbonyl compounds (494). Thus, a convenient procedure was developed for the synthesis of carbonyl compounds (494) from secondary AN (493) through the intermediate terminal BENA (495) (527). 

Condensation of A -acylglycines with carbonyl compounds, the Erlenmeyer synthesis, continues to be exploited to prepare of a wide variety of unsaturated-5(47/)-oxazolones. The reaction is performed in the presence of a cyclodehydrating agent and recently bismuth(lll) acetate has been evaluated in this capacity. Alternatively, unsaturated 5(47/)-oxazolones can be obtained from hippuric acid and a carbonyl compound or from the appropriate dehydroamino acid derivative using 3-(aIkoxycarbonyl)benzotriazole-l-oxides as the cyclodehydrating agent. 

The Mannich reaction [18, 19] is a widely applied means of producing /i-amino carbonyl compounds starting from cheap and readily available substrates. In this reaction an aldehyde 20, an amine 21, and a ketone 22 react in a three-component-one-pot synthesis (Scheme 5.12, pathway 1). As a synthetic alternative, the reaction can also be performed as a nucleophilic addition of a C-nucleophile 22 to a preformed imine 24 which is prepared starting from the aldehyde and an amine source (Scheme 5.12, pathway 2). 

F. A. J. Meskens, Methods for the preparation of acetals from alcohols or oxiranes and carbonyl compounds, Synthesis 1981, 501. 

Tota and Elderfield (248) have described a general synthesis for 2,3-disubstituted and 2,3,6-trisubstituted 5-hydroxypyrazines. In this reaction an a-(bromoacetyl-amino) carbonyl compound (prepared from an a-amino carbonyl compound with... 

Lombardo, L., and Taylor, R.J.K., Silicon in organic chemistry. An improved preparation of a.P-unsaturated acids from carbonyl compounds. Synthesis, 131, 1978. 

The carbonylation of organic compounds catalyzed by organometallic complexes is a useful tool in organic synthesis for the preparation of carbonyl compounds starting from olefins or halogeno compounds. 

Immobilized copper-zeolite Y (Cu-HY) bis(oxazolines) were employed as heterogeneous catalysts in carbonyl-ene and imino-ene reactions, allowing the synthesis of a-hydroxy and a-amino carbonyl compounds 163 from 161 and 162 in satisfactory yields and high enantioselection <04AG(E)1685>. The use of a new, insoluble polystyrene-bound Box ligand (IPB-BOX) was also described with good activity (85-95% ee) <04TA3233>. 

The EGB derived from 2-pyrrolidone promotes (Eq. 27) [18, 19]. The trifluoromethylation of the formation of trihalomethyl anions from trihalo- carbonyl compounds is remarkably useful for the methane and their addition to carbonyl compounds synthesis of fluorine containing compounds. 

The cascade process combining the [Ira(cod)]2-catalyzed vinylation and the Claisen rearrangement was also reported (Scheme 5.35) [35]. This one-pot approach could be applied for the synthesis of Y,S-unsaturated carbonyl compounds 51 from allyl alcohols 49 and vinyl or isopropenyl acetates 50. 

Before we complete the disconnections of carbonyl compounds we shall look at some aspects of control in synthesis as a break from the systematic analysis. 

Olefin synthesis starts usually from carbonyl compounds and carbanions with relatively electropositive, redox-active substituents mostly containing phosphorus, sulfur, or silicon. The carbanions add to the carbonyl group and the oxy anion attacks the oxidizable atom Y in-tramolecularly. The oxide Y—O" is then eliminated and a new C—C bond is formed. Such reactions take place because the formation of a Y—0 bond is thermodynamically favored and because Y is able to expand its coordination sphere and to raise its oxidation number. 

---