Intramolecular hydroalkylation

The use of gold complexes with chiral phosphines to promote asymmetric cyclization reactions remains the most studied approach of several groups.However, Toste and coworkers pushed this chemistry further, when they combined the additive elfects of a chiral phosphine ligand and a chiral counter ion which forms an ion pair with the active species [L Au] X 3> (L = chiral phosphine ligand X = chiral counter ion). Thus a dramatic increase in Au(I)-catalysed enantioselective intramolecular hydroalkylation of... 

Direct intramolecular hydroalkylation of unactivated C=C bonds with a-ketone moieties (113) has been attained for the first time in a reaction catalysed by the Au(I) NHC complex (115), providing a simple access to highly substituted cyclic compounds (114) with good diastereoselectivity. ... 

Sames et al. reported a Sc(OTf)3-catalyzed intramolecular hydroalkylation of isolated electron-deficient olefins (Scheme 43) [95]. Tetrahydropyrans or tetrahy-drofurans carrying C(2)-Iinked a, P-unsaturated malonate side chain 109 and 111 were employed as substrate to furnish the spiroether product 110 and 112 in excellent yields. Notably, germinal substitution along the olefin tether was not required for efficient annulation for the reason that benzylidene malonate activated by Sc(OTf)3 were reactive enough, thus higher conformational rigidity to increase the reactivity of hydride acceptor was not indispensable [96]. 

Gold-activated allene can also be employed as hydride acceptor. Gagosz et al. demonstrated that a phosphite gold complex 154-catalyzed intramolecular hydroalkylation of allenes 151, which afforded the spiro compound 152 and undesired fused bicyclic compound 153 in 30 and 61 % yields, respectively (Scheme 56) [128]. The selectivity could be reversed if HNTfa was exploited. 

Scheme 58 BF3-Et20-catalyzed intramolecular hydroalkylation of isolated oi,P-enals...

The intramolecular hydroalkylation of enones could be readily implemented as well via this strategy (Scheme 63) [38]. The addition of ethylene glycol had a dramatic effect on the reaction rate as demonstrated in the cyclization of enones 168 the reaction could be completed within 12 h, furnishing the cyclized products... 

This section summarizes the most studied organic reactions catalyzed by zeolites and mesoporous aluminosilicates useful in the synthesis of flavoring compoxmds, in perfumery, and other industrial fields. Acetalization reactions of aldehydes/ketones and the intramolecular hydroalkylation of xmsatxxrated alcohols or tandem reactions such as Claisen rearrangement and subsequent intramolecxxlar hydroxyalkylation of olefins are some of the noted reactions. 

In a mechanistic paper, the authors provide evidence that in the first step the vinylphosphane is coordinated to the metal and that the hydroalkylation step then takes place in an intramolecular manner. While the reaction of [ (j7 -C5Me4CF3)RhCl(M-Cl) 2] with diphenylvinylphosphane in chloroform gave a ligand complexation product only, chelate 392 was obtained in 29% yield, when the reaction was carried out in ethanol. 392 was characterized by X-ray crystallography. ... 

---