Table 2.

Synthesis of diethyl 4-alkyl-2,2-oxetane dicarboxylates.

Entry	X	Y		Yield8 [%][a]	Yield9 [%][b]
1	Br	CH2OBn	a	67	89
2	Br	CH2OPh	b	92	65
3	Br	CH2Br	c	51[c]	81
4	Br	CH2Cl	d	80	45/7 (Y=Cl/Br, 9 d/9 c)
5	Cl	CH2Cl	e	86	77 (9 d)
6	Cl	CH2OiPr	f	97	75
7	Cl	CH2OTBS	g	65	71
8	Br	CF3	h	28[d]	43
9	Br	CH3[e]	i	98[f]	82[g]

^[a] O=H insertion conditions: 7 (1.0–3.0 mmol), 1 (1.5 equiv), [Rh₂(OAc)₄] (0.5 mol %), PhH, 0.1 m, 80 °C.

^[b] Cyclization conditions: 8 (0.4–1.0 mmol), NaH (1.2 equiv), DMF, 0.025 m, 25 °C, 16 h.

^[c] Heated at 80 °C for 3 d.

^[d] Yield over two steps from 3-bromo-1,1,1-trifluoroacetone.

^[e] From technical grade 1-bromo-2-propanol (7 i) containing 20 wt % 2-bromo-1-propanol.

^[f] Mixture of regioisomers (4:1).

^[g] Mixture of regioisomers (4-Me/3-Me oxetanes 5.4:1). Bn=benzyl, TBS=tert-butyldimethylsilyl.