Rearrangements diisobutylaluminum hydride

Synthesis of P-Keto Sulfoxides. Optically active p-keto sulfoxides are very useful building blocks (eq 4) because they can be stereoselectively reduced to afford either diastereomer of the corresponding p-hydroxy sulfoxide under appropriate conditions (Diisobutylaluminum Hydride or Zinc ChloridefDlBALf and thus give access to a wide variety of compounds chiral carbinols by desulfurization with Raney Nickel or LithiumJethyhmme ini the case of allylic alcohols epoxides via cyclization of the derived sulfonium salt butenolides by alkylation of the hydroxy sulfoxide 1,2-diols via a Pummerer rearrangement followed by reduction of the intermediate. ... 

The reductive Beckmann rearrangement of oximes has been effected with several types of aluminum hydride reagents. Early examples exhibited only moderate regioselectivity, giving mixtures of primary amines and rearranged secondary amines. Recently, diisobutylaluminum hydride was reported to be most satisfactory for this type of transformation (equation 20). Here dichloromethane is the solvent of choice, and attempted use of ethereal solvents results in the formation of a mixture of primary and secondary amines. ... 

An unexpected reductive rearrangement was observed in the reaction of the dioxime (33) with diisobutylaluminum hydride in dichloromethane, leading to the diamine (34 equation 21). It should be noted that attempted reaction of (33) under various Beckmann rearrangement conditions resulted either in extensive decomposition or fragmentation. 

N.S. Mani and co-workers utilized the organoaluminum promoted modified Beckmann rearrangement during their efficient synthetic route to chiral 4-alkyl-1,2,3,4-tetrahydroquinoline. (4R)-4-Ethyl-1,2,3,4-tetrahydroquinoline was obtained by rearrangement of the ketoxime sulfonate of (3R)-3-ethylindan-1-one. The resulting six-membered lactam product was reduced to the corresponding cyclic secondary amine with diisobutylaluminum hydride. 

Schinzer and Langkopf (83) reported in 1994 their synthesis of various seven- and eight-membered iV-heterocyclic systems resembling the benza-zepine framework of cephalotaxine (Scheme 49) by means of tandem Beckmann rearrangement-allylsilane cyclization. Treatment of compounds 286 and 287 with diisobutylaluminum hydride yielded the heterocycles 288 and 289, respectively. [See Note Added in Proof, p. 264.]... 

The complex is obtained from tri-n-butylphosphine and copper(I) hydride, prepared by reduction of copper(I) bromide with diisobutylaluminum hydride at —50°. The complex is a useful reducing agent it reduces iodobenzene to benzene (80% yield) and benzoyl chloride to benzaldehyde (50% yield). In addition the complex reduces primary, secondary, and tertiary alkyl-, vinyl-, and arylcopper(l) compounds to the corresponding hydrocarbons in high yields, under mild conditions and with no rearrangements.1... 

Substituted Claisen substrate 1 containing an oxygen at C-5 rearranges to an intermediate 1,4-dicarbonyl compound, which undergoes facile lactonization to give 2. Lactone 2 is transformed to cyclopentenone 3 by reduction with diisobutylaluminum hydride and subsequent treatment with a mild base87. 

Ester 775a has been used as an intermediate in synthesizing substrates that produce 1,2-asymmetric induction in the ketene Claisen rearrangement of allylic sulfides [220] (Scheme 104). Reduction of 775a with diisobutylaluminum hydride gives allylic alcohol 776 (> 94% de). Conversion to thioether 111 is accomplished with thiolacetic acid under Mitsunobu conditions this is followed by saponification of the resulting S-acetyl intermediate and alkylation with isopropyl bromide. 

Partial reduction of the two ester groups in 4 with diisobutylaluminum hydride in toluene-hexane at —78 °C provides in situ a dialuminate which, as an aldehyde equivalent, reacts under Wittig—Homer conditions to provide good yields of the diolefin 24. Subsequent conversion of 24 to (4i ,5i )-l,8-(bisbenzyloxy)-2( ),6(E)-octadien-4,5-diol (25) provides the essential framework for a palladium(II)-catalyzed [3,3]-sigmatropic rearrangement to 2S,1S) 2,7-(bisacetoxy)-l,8-(bisbenzyloxy)-3(j, 5( )-octadiene (26) (Scheme 6). The orginal chirality is completely translated into the dissymmetric 3,5-octadiene framework, which has C2 chirality [18]. 

N-Boc leucine was converted to an acid chloride by treatment with isobutyl chloroformate. Subsequent treatment with diazomethane gave the diazoketone (6.241), which was treated with silver benzoate. This led to a Wolff rearrange-mentl40 and formation of 6.242. I ll Reduction of the ester moiety to an aldehyde with diisobutylaluminum hydride allowed condensation with the lithium enolate of ethyl acetate to give 6.243. Saponification led to N-Boc-5-amino-3-hydroxy-7-methyloctanoic acid (6.244, given the pseudonym AHM0A).1 H Amino acid... 

Alkylative Beckmann rearrangements of oxime sulfonates are promoted by trialkylaluminums. The rearrangements give the imines, which are reduced with Diisobutylaluminum Hydride to the corresponding amines (eq 14). Related alkylative Beckmann fragmentations have also been reported. ... 

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