Resin cleavage using DIBAL

Starting from oxygen-linked 1,3-dicarbonyl compounds (malonates or acetoacetates), Tietze and co-workers have demonstrated an allylic substitution at the a-position of varions snbstrates (aUyl acetates, carbonates, and chlorides). Under the conditions employed, bisalkylation was observed in all cases. Since the acetoacetates could be alkylated by hard electrophiles at the y-position, a broad spectrum of compounds might be obtained. The cleavage from the resin was performed using DIBAL-H to obtain the corresponding diols (Scheme 24). 

Aldol condensation of the zinc enolate of resin-bound alkyl ester 29 with aromatic aldehyde or ketone forms a P-hydroxy ester, which upon treatment with DIBAL-H leads to simultaneous reduction and cleavage of the ester moiety from the resin to give a soluble 1,3-diol 31 [31], Parallel synthesis utilizing three ester and nine carbonyl building blocks afforded a library of 27 analogs which was screened for antioxidative efficiency using a ferric thiocyanate assay. 

S LiAIH4 O-OTh.n W v-sN NHAc r [26] DIBAL has been used in the reductive cleavage of resin-bound esters to alcohols Alkenes and alkynes can both be reduced. Other reductions include nitrile to amine. diazo to hydrazine disulfide to thiol epoxide to alcohol [26, 63] [67.74] [123] [158] [180] [227] [251] [274-276]... 

Kamal and co-workers have reported a new approach for the solid-phase synthesis of the pyrrolo[2,l-c][l,4]benzodiazepines 102 using a thiol Wang resin. The interesting feature of this approach was the reductive cleavage and cyclization achieved in the last step on reaction with DIBAL-H yields of the products 102 ranged from 57% (R = 7-OMe, 8-OBn) to 65% (R = H) <04TL7667>. 

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