Dithians Alkylation

Diethyl-3,5-octadiene 174 Dithiane oxides alkylation of 84 carbanions of 84 Dithianes alkylation of 76,79 as acyl anion equivalents 75 carbanions of 76,79 cleavage of 14-18.76,79 desulfurization of 78 oxidation of 23... 

Dithiane alkylation, acyl anion equivalent, Sn2, R must be I ° or 2=... 

Table 2.8 Attempts for the dithiane alkylation with (Z, )-dienylchloride...

Lithium l,3-dithian-2-ides (p. 6, 8) may be alkylated with alkyl bromides or iodides. Steric hindrance is usually of little importance and the resulting ketone can be easily liberated by hydrolysis (D. Seebach, 1969). 

The (V-methyldihydrodithiazine 125 has also been used as an effective formyl anion equivalent for reaction with alkyl halides, aldehydes, and ketones (77JOC393). In this case there is exclusive alkylation between the two sulfur atoms, and hydrolysis to give the aldehyde products is considerably easier than for dithianes. However, attempts to achieve a second alkylation at C2 were unsuccessful, thus ruling out the use of this system as an acyl anion equivalent for synthesis of ketones. Despite this limitation, the compound has found some use in synthesis (82TL4995). 

In this way, product 111 from the first alkylation (2 equiv.) is sequentially treated with HMPA and (+)-epichlorohydrin to afford the bis-dithiane carbinol 116 with construction of four carbon-carbon a bonds in one flask (Scheme 8.31) [56a]. 

Similarly, in another example, alkylation of 111 with diepoxide (—)-115 (1 equiv.) in the presence of HMPA (1.3 equiv.) furnished diol (+)-117. Protection of (+)-117 to form the acetonide, removal of the silyl protecting groups (TBAF), and hydrolysis of the dithiane with Hg(Cl04)2 provided the diketone (+)-118. Hydroxy-directed syn-reduction of both carbonyl groups with NaBI U in the presence of Et2BOMe, and triacetonide formation, followed by hydrogenolysis and monosilylation, afforded the desired Schreiber subtarget (+)-119, which was employed in the synthesis of (+)-mycoticins A and B (Scheme 8.31) [56b]. 

L//-Indole, 3<2-phenyl-l, 3-dithian-2-yl), 10 Indoles, 34 Indoles, 3-acyl-, 8 Indoles, 3 -alkyl, 8 Isocyanate, chlorosulfonyl [Sulfuryl chlonde isocyanate], 41 Isocyanate,2-propyl- [Propane, 2-iso-cyanato-], 96... 

Carlson and Helquist410 were the first to perform the alkylation of 2-lithio 1,3-dithian-S-oxide 323 (equation 180). The yields of this reaction appeared, however, to be low. In spite of the fact that dithian-S-oxides have been intensively investigated268-411, their synthetic applications are rather limited. 

Cyclic dithioketals and acetals represent another important class of sulfur containing chiral auxiliaries, which are available in chiral form by biooxidation. Biotransformations were performed on a preparative scale using whole-cells (wild type and recombinant) and isolated enzyme. Again, enantiocomplementary oxidation of unsubstituted dithianes (linear and cyclic, R = H) was observed when using and CPMOcomo (Scheme 9.28) [211,212]. Oxygenation of functionalized substrates (R = substituted alkyl) with gave preferably trans... 

Dithianes can be alkylated if a proton is first removed by treatment with butyllithium in Since 1,3-dithianes can be prepared by treatment of an... 

Alkylation and hydrolysis of imines alkylation of aldehydes 10-107 Alkylation and hydrolysis of dithianes 10-108 Alkylation and hydrolysis of oxazines and similar compounds 10-109 Reaction of diazo aldehydes with boranes... 

---