Synthesis of Rings with Two Heteroatoms

Diazetidinones 487 were obtained in high yield (75-100%) by the decomposition of diazo compounds 488 in the presence of Rh2(OAc)4 in refluxing benzene. This result is rationalized in terms of an intramolecular carbenoid insertion into the y-NH bond [85TL3171 87JCS(P1)899], 

Carbene species, generated by thermolytic, photolytic, or Rh(II)-catalyzed decomposition of a-diazo-j8-ketophosphonatoamidates 489, insert into the tertiary C—H bond of an N-isopropyl group to give 1,2- 

A series of four-membered Si- or P-containing heterocycles was produced in various yields by electrocyclization or [2-t-2]-dimerization of compounds with multiple carbon-silicon or carbon-phosphorus bonds. These unsaturated species are formed under photolysis of diazo compounds containing a P or Si atom in an a position with respect to the diazo group, following a [l,2]-sigmatropic shift in the intermediate carbene. 

It was reported that trimethylsilyldiazomethane 492 thermolytically (440°C, 10 torr) (75TL2061) or under FVP conditions (750°C) (86JA7849) produces a carbene that isomerizes to 1,1,2-trimethylsilene 493, thereby furnishing the head-to-tail dimer 494 in 40% yield. Silene generated from disilanyl a-diazoacetate 495 in the presence of 7-norbornanone affords 38% of adduct 496 (82JA6830). 

Photolysis of disilanyl a-diazoketones 497 leads through the sequence involving silyl carbene formation followed by rearrangement to acyl sil-enes and their facile cyclization to give l-oxa-2-sila-3-cyclobutenes 498 (84JA1486 88CC72 90CB589). 

---