Olefin addition, Markovnikov with amines

Catalysts for tfie additions of amines to vinylarenes have also been developed. These catalytic reactions include some of the first hydroaminations of unstrained olefins catalyzed by late transition metals, as well as examples catalyzed by lanthanide complexes. These additions occur with Markovrukov selectivity with one set of catalysts and with anti-Markovnikov selectivity with several others. These additions occur by several different mechanisms that are presented in Section 16.5.3.2. 

Terminal alkynes Ar C=CH undergo a Markovnikov hydroamination with amines Ar NHR in the presence of (C6F5)3B as a catalyst to give enamines Ar N(R)C(Ar )=CFl2. The reaction is believed to involve a frustrated Lewis pair (FLP). ° An FLP has also been implicated in the addition P-, N-, C-, and H-based nucleophiles to olefin-tethered boranes. ... 

Allyl p-tolyl sulphoxide 535 reacts with sodium methoxide in methanol by initial prototropic isomerization and subsequent addition of methanol to give 536 (equation 333). Protic solvents are photochemically incorporated by the open chain olefinic bond of trans methyl )S-styryl sulphoxide 537 in a Markovnikov regiospecificity (equation 334). Mercaptanes and thiophenols add to vinyl sulphoxides in a similar manner (compare also Reference 604 and Section IV.B.3) to give fi-alkylthio(arylthio)ethyl sulphoxides 538 (equation 335). Addition of deuteriated thio-phenol (PhSD) to optically active p-tolyl vinyl sulphoxide is accompanied by a low asymmetric a-induction not exceeding 10% (equation 336) . Addition of amines to vinyl sulphoxides proceeds in the same way giving )S-aminoethyl sulphoxides in good to quantitative yields depending on the substituents at the vinyl moiety When optically active p-tolyl vinyl sulphoxides are used in this reaction, diastereoisomeric mixtures are always formed and asymmetric induction at the p- and a-carbon atoms is 80 20 (R = H, R = Me) and 1.8 1 (R = Me, R = H), respectively (equation 337) ... 

Hosokawa, Murahashi, and coworkers demonstrated the ability of Pd" to catalyze the oxidative conjugate addition of amide and carbamate nucleophiles to electron-deficient alkenes (Eq. 42) [177]. Approximately 10 years later, Stahl and coworkers discovered that Pd-catalyzed oxidative amination of styrene proceeds with either Markovnikov or anti-Markovnikov regioselectivity. The preferred isomer is dictated by the presence or absence of a Bronsted base (e.g., triethylamine or acetate), respectively (Scheme 12) [178,179]. Both of these reaction classes employ O2 as the stoichiometric oxidant, but optimal conditions include a copper cocatalyst. More recently, Stahl and coworkers found that the oxidative amination of unactivated alkyl olefins proceeds most effectively in the absence of a copper cocatalyst (Eq. 43) [180]. In the presence of 5mol% CUCI2, significant alkene amination is observed, but the product consists of a complicated isomeric mixture arising from migration of the double bond into thermodynamically more stable internal positions. 

Metal-catalyzed oxidative addition of nitrogen nucleophiles such as amines and amides to olefins represents a straightforward atom economical approach for the preparation of enamines and enamides, respectively. These aminatimi processes may proceed with Markovnikov or anti-Markovnikov regioselectivity and in the latter case such products can be obtained as either or Z isomers (Scheme 1). Therefore, the ability of the catalyst to control that regiochemistry and stereoselectivity constitutes a chaUenging issue for synthetic chemists. 

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