The olefinic aldol reaction. Intramolecular cyclization forming five- and six-membered rings

Carbozincation Reactions of Carbon–Carbon Multiple Bonds

“…N,N-Dimethylhydrazones of alkenyl ketones also undergo carbocyclization when deprotonated and transmetalated to provide the butylzinc aza enolate (Scheme 93). 127 However, the diastereoselectivity of this carbocyclization is only fair (cis/trans, 88:12). Both 5-exo and 6-exo products can be accessed using this method.…”

Carbometallation Reactions

“…In all cases, the carbometallated product can be functionalized with various electrophiles [174]. N,N-dimethylhydrazones of v-alkenyl ketones also undergo carbocyclization upon deprotonation and transmetallation into BuZn(II) cation (see Scheme 7-143) [175].…”

“…The stereoselectivity has been explained by a chair-like transition state in which the electrophilic double bond occupies a pseudo-axial position (the zinc (Z)-a-aminoenolate and the double bond are gauche to each other), as depicted in Scheme 7-144 [176]. Scheme 7-143 Intramolecular carbocyclization of a zincated N,N-dimethylhydrazone and an v-alkenyl ketone [175].…”

“…Although much slower, the 6-exo-trig-cyclization of an a-zincated ketone hydrazone led to the cyclic derivative in good yield with a diastereoselectivity of 91/9 [175]. The addition reaction of an a-zinc hydrazone to, e. g., unsubstituted ethylene, was performed under pressure for four days at 35 hC, and led to the carbometallated intermediate 237-ZnBu which, upon hydrolysis (or deuterolysis) gave the product 237 in 88 % yield (Scheme 7-145) [177].…”

Controllable Cyclization Reactions of 2‐(2′,3′‐Allenyl)acetylacetates Catalyzed by Gold and Palladium Affording Substituted Cyclopentene and 4,5‐Dihydrofuran Derivatives with Distinct Selectivity

“…On the other hand, the ene reaction between an enol and an alkyne is a well‐established synthetic reaction with respect to its carbon‐ring‐forming variant, which is known as the Conia reaction 5. In addition to the thermal Conia reactions, which were usually carried out under harsh conditions, such as at high temperatures or in the vapor phase,5 [In(NTf 2 ) 3 ] (Tf=trifluorosulfonyl),6a Au I ,6b,f,g Pd II ,6c,e Ni(acac) 2 with Yb(OTf) 3 ,6d [CoCp(CO) 2 ] (Cp=cyclopentadienyl),6h,m CuI,6i TiCl 4 ,6j [Mo(CO) 5 (NEt 3 )],6k and ZnBr 2 6l have been reported as the catalysts. Widenhoefer et al.…”