Regioselectivity in Diels—Alder Reactions of Thiazolo[3,2‐d][1,4,2]diazaphospholes and Related Compounds.

Abstract

Organo-phosphorus compounds S 0080 Regioselectivity in Diels-Alder Reactions of Thiazolo[3,2-d][1,4,2]diazaphospholes and Related Compounds. -A variety of title diazaphospholes undergo Diels-Alder reactions with dienes (II) at the C=P double bond. In the case of isoprene (IIb) the reactions proceed regioselectively. In contrast, 1,3-azaphosphole (XIV) exhibits reduced reactivity and reacts with dienes only in the presence of oxidizing agents. -(BANSAL, R. K.; KARAGHIOSOFF, K.; GUPTA, N.; KABRA, V.; MAHNOT, R.; SHARMA, D. C.; MUNJAL, R.; KUMAWAT, S. K.; Z. Naturforsch., B: Chem. Sci. 60 (2005) 1, 7-14; Dep. Chem., Univ. Rajasthan, Jaipur 302 004, India; Eng.) -Klein 24-156

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

“…In view of this, the 13 C NMR spectrum of a representative product 8a was recorded. The signals of the carbon atoms directly bonded to the phosphorus atom, namely C1 (δ = 132.7 ppm, 1 J PC = 36.0 Hz), C3 (δ = 54.5 ppm, 1 J PC = 31.7 Hz) and C9 (δ = 33.6 ppm, 1 J PC = 44.5 Hz) are identified readily by large values of 1 J PC [33–34]. The 13 C NMR signals due to the O -menthoxy moiety were assigned on the basis of the reported results [35].…”

Diels–Alder reactions of 5,6-dihydrothiazolo[3,2-d][1,4,2]diazaphospholes: A DFT investigation

“…Similarly, the exclusive formation of the meta regioisomer (P/Me, 1:3) in the DA reaction of 3-methoxycarbonyl-5,6-dihydrothiazolo[3,2-d][1,4,2]-diazaphosphole (1b) with isoprene [16] can be rationalized on the basis of the SMO interactions observed in the HOMO of the transition structure TS 7 (Fig. 4).…”

“…Experimentally, we have observed earlier that 3-alkoxycarbonyl-5,6-dihydrothiazolo[3,2-d][1,4,2]diazaphosphole exhibits complete endo stereoselectivity in its DA reactions [16]. Furthermore, meta regioproduct (P/Me, 1:3) was formed exclusively in its reaction with isoprene.…”

“…These reactions could be accomplished under microwave irradiation in much shorter time without affecting the stereoand regioselectivities [15]. The DA reactions of thiazolo [3,2-d][1,4,2]diazaphospholes and their 5,6-dihydro-and benzo-derivatives and those of 1,3-azaphospholo [5,1-b]benzothiazole occur with complete endo stereoselectivity, and in the reaction with isoprene, 70-100% regioselectivity is observed [16]. [1,4,2]Diazaphospholo [4,5-a]pyridines follow a similar course in their DA reactions with 2,3-dimethylbutadiene and with isoprene, 80% regioselectivity being observed in the latter case [17].…”

“…We have now computed the DA reactions of the 6 aromatic system, 5,6-dihydrothiazolo[3,2-d]-[1,4,2]diazaphospholes with 1,3-butadiene and with isoprene at DFT level (B3LYP/6-311++G * * //B3LYP/6-311G * * ) to evaluate origin of the stereo-and regioselectivities reported experimentally [16] and also to compare the activation energy barriers with those for the 10 aromatic, thiazolo[3,2-d][1,4,2]-diazaphospholes and acyclic phosphaethene.…”