Aluminum compounds conjugate substitution

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

The first completely conjugated [/i,/] 1,4-diazocine (112, R -R = H) was synthesized by Perlmutter from OPD and o-dibenzoylbenzene, using aluminum chloride as catalyst (68CC1202). Improved yields of the parent 112 and substituted derivatives were realized by Olliero and Solladie (75S246). Solladie and co-workers prepared and resolved dissymmetric derivatives of 112 (R -R = H, Me and R = R = R = R = H, R = CHO) and 113 as part of stereochemical studies of these compounds (78JCR(S)408) (see Section III). 

Malonate and related activated methylene compounds have also been used as the nucleophile in conjugate addition/Michael reactions. Taylor and co-workers have developed a new methodology that utilizes (salen)aluminum complexes such as 43 as a catalyst to effect the enantioselective conjugate addition to a,p-unsaturated ketones by a variety of nucleophiles.25 For example, nitriles, nitroalkanes, hydrazoic acids, and azides have found utility in this reaction. Additionally, cyanoacetate (42) has been demonstrated to undergo a highly enantioselective conjugate addition to 41. The Krapcho decarboxylation is then necessary to produce cyanoketone 44, an intermediate in the synthesis of enantioenriched 2,4-cw-di substituted piperidine 45. 

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