Stereochemistry carbon

Insertion into the carbon-mercury bond proceeds with retention of the carbon stereochemistry - . 

Regioseiectivity Markovnikov s ruie is foiiowed. X bonds to the iess substituted carbon. Stereochemistry Anti addition occurs. 

Mechanism Type Species Adding to ML Number of steps Stereochemistry at carbon Stereochemistry of new ligands on the metal... 

A backside attack of C02> on the alkyl carbon, analogous to the SO2 insertion mechanism was ruled out by studies of the a-carbon stereochemistry upon insertion (25). The insertion of CO2 into the metal carbon bond of threo-cis-W(CO) (L)(CHD-CHD-Ph) (L = CO and PMc3) proceeds with retention of configuration at the a-carbon (Scheme 1) (26). This is in contrast to the inversion of configuration at the alpha carbon found in backside SO2 insertion reactions. 

Since DFRC does not scramble the (5-carbon stereochemistry, the recovery of optically inactive (5-5 (Figure 2.10d) and (5-(5 DFRC dimers very elegantly confirmed the racemic nature of lignins [99]. The isolation of novel arylisochroman trimers from DFRC-degraded loblolly pine wood sample supports the occurrence of... 

Geometric isomers of linear quadridentate ligands on octahedral compounds are recognized to exist in one trans and two ois forms (see Figure 3). The ois compounds are generally referred to as the a and B forms. In these examples we can see that the terminology developed to denote the relatively simple tetrahedral and planar carbon stereochemistry is not adequate when applied to the stereochemistry of octahedral compounds. 

The carbon atoms not at the ends of the stack have a half-planar or bntterfly-type disposition of their fonr bonds (Fig. 12.2). This makes them members of the unconventional non-tetrahedral assortment of tetracoordinate carbons to which also belong planar, pyramidal, and propellane (umbrella) carbon (Fig. 12.2 references to these carbon stereochemistries and to half-planar carbon in organometallic compounds, are given in [1]). Thns they excite the same kind of curiosity as that engendered by the planar carbon of Chapter 1 and the pyramidal carbon of Chapter 2. 

The use of alkyl halides has given rise to the question of control of the carbon stereochemistry configuration. The concerted mechanism (CM) would lead to retention of configuration whereas the dissociative pathway being assimilated to a Sn2 would lead to inversion. The experimental conditions (nature of the halide, solvent, steric congestion) have a major influence on the Sn2 mechanism [32]. The nature of the nucleophile, namely the donating character of the phosphines bound to the metal must also be considered. 

Tosylate Formation with Inversion of Configuration. Alkyl tosylates can be formed directly from secondary alcohol functionality with retention of carbon stereochemistry by treatment withp-Toluenesulfonyl Chloride and Pyridine. However, conversion of an alcohol to the corresponding tosylate of opposite stereochemistry typically requires a minimum of three steps. For example, inversion of the stereocenter with benzoic acid under Mitsunobu reaction conditions, hydrolysis of the resulting ester, and finally conventional tosylation of the alcohol, provides an attractive route for this transformation. A similar route, the inversion of a secondary alcohol directly with p-TsOH, Diethyl Azodicarboxylate (DEAD), and Triphenylphosphine, does not produce the desired tosylate product. ... 

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