Alkenyl trichloroacetate

Since the use of stoichiometric amounts of organostannane is unfavorable for the environment, they have established reaction conditions for a process that is catalytic in organostannane. Thus, the reaction with an alkenyl trichloroacetate as the precursor of the tin enolate in the presence of the catalytic amount of Me3SnOMe and the appropriate aldehydes afforded the corresponding aldol adducts with high enantio-and diastereoselectivities (Table 9.8).17 However, when the aliphatic aldehydes were used as substrates, the reaction did not take place at all. The proposed catalytic cycle is shown in Figure 9.3. It was also demonstrated that this catalytic system could be applied using a [3-lactone compound as an alkenyl trichloroacetate equivalent to... 

By use of chelating tri- and tetramines 59 or 60 Kharasch additions can be performed in 65-75% yield using 0.3-10 mol% FeCl2 as the catalyst (Fig. 13) [116, 117]. The same catalysts are very efficient to promote otherwise difficult ATRC of co-alkenyl trichloroacetates 58 providing five-membered lactone 61 by 5-exo cycli-zation in 55% yield and eight- to ten-membered lactones 62 by 8-10-endo cyclizations in 34-50% yield, respectively. Even oo-allyl oligo(ethyleneoxy) trichloroacetates underwent radical macrolactonization reactions in 56-60% yield with 10 mol% of catalyst. 

Speckamp et al. have reported the synthesis of medium-ring lactones by Cu(bipy)Cl-catalyzed cyclization of alkenyl trichloroacetates. In the case of 5-hexenyl trichloroacetate (175), a 0.06 M solution in a sealed tube at 190°C gave the trichlorolactone (176) in fair yield (Equation (15))... 

In analogy t 0 the Cu(II) complex systems, the silver(I) -catalyzed aldol reaction is also proposed to proceed smoothly through a Lewis acidic activation of carbonyl compounds. Since Ito and co-workers reported the first example of the asymmetric aldol reaction of tosylmethyl isocyanide and aldehydes in the presence of a chiral silver(I)-phosphine complex (99,100), the catalyst systems of sil-ver(I) and chiral phosphines have been applied successfully in the aldol reaction of tin enolates and aldehydes (101), Mukaiyama aldol reaction (102), and aldol reaction of alkenyl trichloroacetates and aldehydes (103). In the Ag(I)-disphosphine complex catalyzed aldol reaction, Momiyama and Yamamoto have also examined an aldol-type reaction of tin enolates and nitrosobenzene with different silver-phosphine complexes (Scheme 15). The catalytic activity and enantioselectivity of AgOTfi(f )-BINAP (2 1) complex that a metal center coordinated to one phosphine and triflate were relay on solvent effect dramatically (Scheme) (104). One catalyst system solves two problems for the synthesis of different O- and AT-nitroso aldol adducts under controlled conditions. 

The successful use of the silver complex formed from an iso-leucine-derived phosphine (L2 in Scheme 11.4) as catalyst for the multicomponent Mannich reaction of silyl enol ethers 10 with in situ formed aliphatic imines allowed its application in the enantioselective synthesis of the alkaloid sedamine (56% yield, 98% ee) [17]. Also cyclic and acyclic alkenyl trichloroacetates (10, Z = EtOCO) can be used in the reaction with ethyl glyoxylate and diverse aniline derivatives 11 catalyzed by... 

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