Studies in organophosphorus chemistry

Tertiary Phosphane/Tetrachloromethane, a Versatile Reagent for Chlorination, Dehydration, and PN Linkage

“…Again only about 50% of the nitrile is formed as shown in eq. (42), the other half being formed by dehydration of the dichlorophosphorane (6) occurring as an intermediate via a B mechanism. For this partial reaction eq.…”

Bromination and Accompanying Rearrangement of the Polycyclic Oxetane 2,4-Oxytwistane

“…22,76,77 For example, oxiranes react with CCl 4 /Ph 3 P to form vicdichlorides. 76,77 An extension of this approach has been achieved using CBr 4 /Ph 3 P with oxetane and oxolane homologues yielding α,ω-dibromo compounds, as described in a previous report. 22 The [Ph 3 P(CBr 3 )] + Br − brominating agent is milder than reagents used in traditional methods, 22,61,78 such as HBr/HOAc or PBr 3 .…”

“…The active reagent in Appel/Corey–Fuchs reactions is triphenyl(trihalomethyl)phosphonium halide ([Ph 3 P(CX 3 )] + X – ; X = Cl, Br). , The brominating agent is formed in situ from a preequilibrated admixture of tetrabromomethane (CBr 4 ) and triphenylphosphine (Ph 3 P) (Scheme ). , The substrates for which the Appel − and Corey–Fuchs − reaction conditions are commonly used are alcohols, oximes, aldehydes, or ketones. Cyclic ethers can also be converted into their respective α,ω-dihalo compounds in this manner. ,, For example, oxiranes react with CCl 4 /Ph 3 P to form vic -dichlorides. , An extension of this approach has been achieved using CBr 4 /Ph 3 P with oxetane and oxolane homologues yielding α,ω-dibromo compounds, as described in a previous report . The [Ph 3 P(CBr 3 )] + Br – brominating agent is milder than reagents used in traditional methods, ,, such as HBr/HOAc or PBr 3 . − Oxetane 2 was thus subjected to 2 equiv of CBr 4 /Ph 3 P in lieu of the aforementioned reagents to avoid possible complications.…”

“…Cyclic ethers can also be converted into their respective α,ω-dihalo compounds in this manner. 22,76,77 For example, oxiranes react with CCl 4 /Ph 3 P to form vicdichlorides. 76,77 An extension of this approach has been achieved using CBr 4 /Ph 3 P with oxetane and oxolane homologues yielding α,ω-dibromo compounds, as described in a previous report.…”

Organocatalytic Stereospecific Appel Reaction

“…Under these conditions, ( R )-styrene oxide (( R )- 5a ) could be converted to the respective dichloride ( S )- 6a in a good yield of 92% with an excellent er of 96:4. Thakore et al showed that the initial ring opening of epoxides in a dichlorination occurs on the most substituted carbon . This might be the reason for the excellent er achieved in the chlorination of styrene oxide ( R )- 5a , whereas the substitution of benzylic alcohol ( R )- and ( S )- 2q led to lower enantiomeric ratios.…”