Heteroatom nucleophiles additions

Chlorohydrin 61 is formed by the nucleophilic addition to ethylene with PdCl2 and CuCl2[103,104]. Regioselective chlorohydroxylation of the allylic amine 62 is possible by the participation of the heteroatom to give chlorohydrin 63. Allylic sulfides behave similarly[105]. 

Conjugate Addition of Heteroatom Nucleophiles and Subsequent Nef Reaction... 

In his original paper,2 Cram disclosed an alternative model that rationalizes the preferred stereochemical course of nucleophilic additions to chiral carbonyl compounds containing an a heteroatom that is capable of forming a complex with the organometallic reagent. This model, known as the Cram cyclic or Cram chelate model, has been extensively studied by Cram9 and by others,410... 

Addition of heteroatomic nucleophiles to divinyl sulphoxides gives mono and bi-functionalized products as well as compounds resulting from their cyclization. For... 

Heteroatom substituents also introduce polar effects. In the case of a-alkoxy aldehydes the preferred TS appears to be F and G for the E- and Z-enolates, respectively. These differ from the normal Felkin TS for nucleophilic addition. The reactant conformation is believed to be determined by minimization of dipolar repulsion between the alkoxy substituent and the carbonyl group.96 This model predicts higher 3,4-anti ratios for Z-enolates, and this is observed. 

The Michael addition of heteroatom nucleophiles to nitroalkenes (Section 4.1.1) followed by denitration provides a useful method for the preparation of various natural products. 

Cationic Fp (olefin) complexes [Fp = f/5-C5H5Fe(CO)2] undergo regio-specific addition of heteroatomic nucleophiles.32 Subsequent ligand transfer (carbonyl insertion) occurs with retention of configuration at the migrating center (R—Fe—CO -> RCOFe).33 A combination of these processes has provided a novel stereospecific azetidinone synthesis which can also be applied to condensed systems.34... 

Apart from some special cases, the ring-closure step in the course of the synthetic pathway is often condensation reaction and, thus, these transformations can be considered as cyclocondensations . Reactions following a few other mechanisms like cycloaddition, electrocyclization, and intramolecular nucleophilic addition of electron pair of an atom to a multiple bond also occur relatively often. Because of the fairly large complexity of the ring systems belonging to this chapter, the treatment according to the heteroatomic combinations seemed the most straightforward. Thus, the fused... 

Non-heteroatom-substituted carbene complexes are in principle accessible either by electrophilic or by nucleophilic addition to alkynyl or alkenyl complexes (Figure 3.26). 

Concerning the M=Co, bond, most of the reported examples result from inter- or intramolecular additions of anionic nucleophiles containing at least two reactive heteroatoms. Thus, sodium dimethyldithiocarbamate was found to react with the cationic allenylidene [RuTp(=C=C=CPh2)(PPh3)2] [PFg] (76) to generate the alle-nyl-metallacycle 77 (Scheme 26) as the result of the nucleophilic addition of one of the sulfur atoms at the Cq, carbon and subsequent coordination of the second sulfur to the ruthenium center, with concomitant release of a triphenylphosphine ligand [282]. Complex 77 could also be synthesized by treatment of the neutral derivative... 

Nucleophilic additions of alcohols, amines, thiols, and selenols to Group 8 buta-trienylidene intermediates [M]=C=C=C=CR2 have also been used in the preparation of stable heteroatom-conjugated allenylidene complexes. Thus, activation of trimethylsilyl-l,3-butadiyne HC=C-C=CSiMe3 by the iron(II) complex [FeClCp (dppe)], in methanol and in the presence of NaBPh4, resulted in the high-yield formation of the methoxy-allenylidene [FeCp =C=C=C(OMe)Me ... 

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