User:Benjah-bmm27/degree/3/CLW

=S, Se, Si, P, CLW=

Organosulfur electrophiles and sulfoxides

 * Organosulfur compounds, organoselenium chemistry, organophosphorus, organosilicon
 * Sulfur electrophiles: sulfenyl chlorides (RSCl) and organodisulfides (RSSR), e.g. diphenyl disulfide
 * Sulfoxide elimination
 * Carbonyl group (with α and β hydrogens) + LDA → enolate
 * Enolate + PhSSPh → α-thiophenylcarbonyl
 * α-thiophenylcarbonyl + H2O2 → α-sulfinylcarbonyl (a sulfoxide group next to the carbonyl)
 * Sulfoxide + heat → α,β-unsaturated carbonyl (syn elimination of PhSOH)
 * Selenoxide elimination
 * Analogous to sulfoxide elimination

Allylic oxidation

 * Allylic oxidation using catalytic selenium dioxide: R-CH2-CH=CH2 → R-CH(OH)-CH=CH2
 * Selenium dioxide is hydrated to selenous acid: SeO2 + H2O →O=Se(OH)2
 * O=Se(OH)2 + R-CH2-CH=CH2 (allyl compound) → R-CH=CH-CH2-Se(OH)3, a [4+2] cycloaddition like the ene reaction
 * R-CH=CH-CH2-Se(OH)3 eliminates H2O to form the seleninic acid R-CH=CH-CH2-Se(=O)OH
 * R-CH=CH-CH2-Se(=O)OH undegoes a a [3,3]-sigmatropic rearrangement to R-CH(O-Se-OH)-CH=CH2
 * R-CH(O-Se-OH)-CH=CH2 hydrolyses to an allylic alcohol R-CH(OH)-CH=CH2 and Se(OH)2
 * Se(OH)2 oxidised back to SeO2 by tert-butyl hydroperoxide, tBuOOH

Julia olefination

 * Julia reaction: trans-alkenes from sulfones
 * Sulfone + BuLi → sulfone-stabilised carbanion
 * Carbanion + aldehyde or ketone → alkoxide anion
 * Alkoxide ion + Ac2O → acetoxy sulfone
 * Acetoxy sulfone + sodium amalgam (Na/Hg) → alkene
 * Reduction proceeds via long-lived anion formed by elimination of the sulfinate PhS(=O)O−

Sulfur ylids

 * Ketone → epoxide by deprotonating trimethylsulfonium to Me2S=CH2
 * Johnson-Corey-Chaykovsky reaction: carbonyl → epoxide, by a sulfonium ylide (sodium methylsulfinylmethylide (NaDMSO) and dimethyloxosulfonium methylide)

Swern oxidation

 * Swern oxidation: alcohol → aldehyde or ketone, by DMSO, oxalyl chloride, triethylamine

Xanthates etc

 * Dithianes (thioacetals) for carbonyl umpolung - nucleophilic carbonyl C
 * Pummerer rearrangement
 * Tschugaev elimination: preparation of alkenes from dithiocarbonates
 * ROH → RH via reduction of the dithiocarbonate ROC(=S)SMe (AIBN, Bu3SnH, )

Natural organosulfur compounds

 * Penicillins and cephalosporins

Organophosphorus

 * Macrolactonisation with triphenylphosphine and 2,2′-dipyridyl disulfide

Horner–Wadsworth–Emmons

 * Horner–Wadsworth–Emmons reaction
 * Gives trans-alkenes
 * Greater reactivity of the ylid compared to Wittig allows use of stabilised ylids with ketones - not possible in the Wittig reaction
 * Phosphonates are easily made from phosphites by the Arbuzov reaction

Mitsunobu

 * Mitsunobu reaction: ROH → RNu by DEAD, triphenylphosphine and nucleophile, with inversion of configuration (one-pot process)

Organosilicon

 * Allylsilanes as nucleophiles