Homoallylic hydrazines

Alternatively, chiral hydrazones can be prepared from chiral aldehydes, e.g., 161, which underwent addition of allyltrichlorosilane in DMF to give the homoallylic hydrazine 162 with high yield and excellent diastereoselectiv-ity [76] (Scheme 25). 

Homoallylic hydroxylamines and homoallylic hydrazines are synthesized in excellent yields from aldonitrones and hydrazones in aqueous media with allylgallium reagent in the presence of O.lequiv. of NH4G1 or Bu4NBr. The reaction rate can be increased dramatically under microwave activation (Scheme 129).416... 

It was also found that in the presence of a catalytic amount of Sc(OTf)3 benzoylhydrazones reacted with tetraallyltin to afford the corresponding homoallylic hydrazines these were readily converted to homoallylic amines. Three-component reactions of aldehydes, benzoylhydrazine, and tetraallyltin also proceeded smoothly in the presence of a catalytic amount of Sc(OTf)3 [15]. 

Synthesis of homoallylic alcohols through the reaction of organometallic allyl compounds with carbonyl compounds is one of the most important processes in organic synthesis. Sc(OTf)3-catalyzed allylation of aldehydes with tetraallyltin to prepare homoallylic alcohols has been reported. Recently, it was revealed that the addition of acetic anhydride to the reaction mixture dramatically increases the reaction s yields to more than 90% [10]. On the other hand, in the presence of a catalytic amount of Sc(OTf)3 (l-5mol%), benzoylhydrazines reacted with tetraallyltin to give the corresponding homoallylic hydrazines, which were readily converted to homoallylic amines (Scheme 12.6) [11]. Three-component reactions of aldehydes, benzoylhydrazine, and tetraallyltin also proceeded smoothly in the presence of a catalytic amount of Sc(OTf)3. 

Azo-ene reactions. The ene reaction provides a powerful method for C-C bond formation with concomitant activation of an allylic C-H bond. A variety of functionalized carbon skeletons can be constructed due to the range of enophiles which can be used. For example, carbonyl compounds give homoallylic alcohols and imino derivatives of aldehydes afford homoallylic amines. The azo-ene reaction offers a method for effecting allylic amination by treatment of an alkene with an azo-diester to afford a diacyl hydrazine which upon N-N cleavage furnishes a carbamate. Subsequent hydrolysis of the carbamate provides an allylic amine. Use of chiral diazenedicarboxylates provides a method for effecting stereoselective electrophilic amination. 

The acetoxy group was hydrolyzed using hydrazine to give (46). Nucleophilic substitution of the fluorine atom produced the tricyclic p lactam (47). A diastereoselective aza-Diels-Alder reaction was used in a synthesis of (—)-lasubine (I). Tin tetrachloride-mediated reaction of complex (48) with Danishefsky s diene afford 2,3-dihydro-4-pyridone (49) as a single diastereomer (Scheme 86). Chiral benzaldehyde imines can be allylated with high diastereoselectivity to give optically active homoallylic amines (Scheme 87). 

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