Regioselectivity electrophilic ring opening

The gold(I)-catalysed cycloisomerization of 1,6-cyclopropene-enes has been reported to proceed through regioselective electrophilic ring opening of the three-membered ring to... 

The regioselectivity of these ring opening reactions is sensitive to additional annelation on benzene (Table 7). In the tetralin derivative (59), little selectivity between type I and type II products is observed with either set of electrophilic reagents. A reversal of regioselectivity is observed in cyclobutabenzene and indan... 

Aziridines are well-known carbon electrophiles capable of reacting with various nucleophiles, and their ability to undergo regioselective ring-opening reactions... 

The 7-aryl-5-cyanomethyl-l,3-dimethyl-2,4-dioxopyrido[2,3- pyrimidines 458 have been regioselectively synthesized through the nucleophilic attack of the amino groups in 6-amino-l,3-dimethyluracil 452 on the highly electrophilic center at C-6 in 6-aryl-3-cyano-4-methylthio-2//-pyran-2-ones 457. Ring opening of 457 followed by decarboxylation and recyclization with the elimination of methylmercaptan gave 458 with no detection of the 5-aryl-7-cyanomethyl isomers 459 (Equation 38) <20008541 >. 

The electrophilic properties of substituted 6//-l,3-thiazine-6-ones (208) in solution also shows reactivity at C-2 in acidic conditions and at C-6 in basic conditions. The regioselective reaction of 4-ethoxycarbonyl-2-phenyl-6//-l,3-thiazine-6-one with dimethylamine leads, after ring opening and reclosure, to two diasteriomeric 5-dimethylcarboxamido-4-ethoxy-carbonyl-2-phenyl-A2-thiazolines 209 and 210, whose structures were confirmed by X-ray diffraction studies on 210 (Scheme 84) (88BSF897). Com-... 

This chapter reviews the chemical literature of monocyclic aziridines and 2//-azirines from 1995 through 2007. It reveals that aziridines are well-behaved carbon electrophiles capable of reacting with various nucleophiles. The ability of aziridines to undergo regioselective ring-opening reactions contributes largely to their synthetic value. 

The regioselectivity of electrophilic addition to the 3-oxaplatina(II)cyclo-butane complex (89) is very dependent on the nature of the electrophile. Treatment of (89) with the strong electrophile acetyl chloride leads to exclusive attack at the hard metallacycle oxygen [Eq. (29)], to give the ring-opened product... 

Reagents with the six electrones are good electrophiles but rather complex and require controlled reaction conditions (Scheme 5.23). Thiirane in TM 5.11 is therefore conveniently interconverted by one-bond disconnection and regioselective ring opening, and then proper FGI affords styrene as the starting material. Formation of the thiirane ring in TM 5.11 needs more synthetic steps from styrene, bromination, substitution of more reactive benzylic bromine by sulfide anions and cyclization in the last step. 

---