Crotyltitanium compounds

Complete details are available concerning stereoselective addition of these reagents to chiral aldehydes or ketones and of crotyltitanium compounds to carbonyl groups (12, 354).2 The most diastereoselective additions to cyclohexanones known to date are effected with organotitanium reagents. 

Chiral diolato titanium allyls (Scheme 361) have been used in the synthesis of (+)-sedamine in an 11 step procedure in which the allyltitanation reaction is the key step.884 The analogous chiral crotyltitanium compound (Scheme 362) directs the nucleophilic addition to the 6V-face of aldehydes to give a mixture of diastereomeric homoallylic alcohols.885,886... 

Table 5. Chemoselective Addition of Crotyltitanium Reagents to Carbonyl Compounds 90)...

Table 8 Diastereoselective Addition of Various Crotyltitanium(IV) Reagents to Carbonyl Compounds...

Configurational lability is desirable in type III reagents, in as much as one geometric isomer is more reactive and/or highly favored at equilibrium. Ti -Crotyl-chromium, -titanium and -zirconium compounds apparently satisfy these requirements, - while q -crotyltitanium reagents such as dicyclopenta-dienylcrotyltitanium appear to be configurationally stable. ii -Cyclopentadienylcrotylmolybdenum complexes also appear to be stable. ... 

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