Protocols‎ > ‎

Functional Groups

Protecting Groups
Corey-Fuchs reaction
Seyferth-Gilbert homologation
Bestmann reagent
Alkene + Br2
Alkene + ozonolyse (O3 then DMS) (OsO4 then NaIO3 - Lemieux-Johnson reagent:)

Ethynyl glycine synthesis
Starting with aldehyde TL 36 (1995) 877-880, T 52 (1996) 11215-11238
Stille coupling on the acetylene JOC 55 (1990) 4657-4663
Burgess reagent

React carboxylic acid with diphenylphosphoryl azide. In base: Curtius rearrangement. In acid: Schmidt reaction.
React isocyanate with amine to generate urea.
React isocyanate with alcohol to generate carbamate.

Staudinger reduction
To reduce azide groups to amines.
Related are the Staudinger ligation and the azide to diazo reaction (ACIE E. Myers and R. Raines).

Organoselenyl Compounds

(source: Organoselenium Chemistry: a practical approach. Thomas G. Back. OUP NY (1999).
The notorious stench of organoselenium compounds can be minimised by using arylselenyl compounds (due to low vapour pressure.)
Toxic, but seemingly no more so than can be handled by standard PPE (fume hood, gloves, etc.).
C-Se bond is weaker than C-S. Selenoxide is more strongly polarised than sulfoxide. Therefore selenoxide eliminations occur rapidly at -78 to rt, while sulfoxide eliminations require heating to over 100C.
Oxidation of Se(II) to Se(IV) is easy, and further oxidation to Se(VI) is easily avoided (by strength of oxidising conditions.)
Selenyl halides (RSeX) have low lying LUMOs and are soft, powerful electrophiles.
Selenols (RSeH, RSe-) have high HOMOs and are soft, poerful nusleophiles. (therefore proton abstraction rarely competes with Nu attack)
Se stabilises adjacent carbocations and carbanions.
Selenoxides with different substituents are chiral, recently been used in asymmetric synthesis (eg asymmetric allylic oxidation.)

Oxidative a,b-unsaturation of beta-keto esters with py, PhSeCl, H2O2: JACS 97 (1975) 5434-5447; TL 22 (1981) 5301-5302; beta-keto aldehydes: JOC 46 (1981) 2920-2923.
It seems you can't Krapcho decarboxylate between introducing Se and elimination (due to lack of lit. precedent.)


Sharpless AD of chiral compounds
Two options. Catalysed: low yielding but highly diastereoselective. Uncatalysed: no diastereoselectivity, but high yielding and easily separated by CC. Perkin1 (2000) 2465-2473.

TMS-Cl / DIPEA will react with alcohols fast in DMF, slow in DCM (can take hours.) Slower if secondary (can take days.)
TMS-Cl / DIPEA will react with carboxylic acid to TMS ester. Transient protection, falls apart again on workup.
Subpages (1): Docking