Cyclophosphamide, Alvocidib, and Rituximab in Treating Patients With High Risk B-Cell Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma

Inclusion Criteria: * Histologically confirmed chronic lymphocytic leukemia (CLL) or B-cell prolymphocytic leukemia\* (PLL) arising from CLL * Patients must have documented B-cell lymphocytosis \> 5 x 10\^9/L at some point since initial diagnosis of CLL * Patients must have B-cells that co-express CD5 with CD19 or CD20 * Patients who do not have dim sIg or CD23 expression on their leukemia cells should be examined for cyclin D1 over-expression or t(11;14) to rule out mantle cell lymphoma * To be considered high risk, patients must meet the following criteria: * At least 1 of the following: * 17p deletion * 11q deletion * Un-mutated IgV\_H (≥ 98% homology) * Age \> 70 years * B\_2M \> 4 * AND at least 1 of the following: * Progressive or marked splenomegaly and/or lymphadenopathy * Anemia (hemoglobin \< 11 g/dL) or thrombocytopenia (platelets \< 100,000/mm\^3) * Weight loss exceeding 10% of body weight over preceding 6 months * NCI grade 2 or 3 fatigue * Fevers \> 100.5° F or night sweats for \> 2 weeks without evidence of infection * Progressive lymphocytosis, with an increase exceeding 50% over a 2-month period or a doubling time of \< 6 months * No other concurrent hormones, chemotherapy, or radiotherapy except for steroids for new adrenal failure or hormones for nondisease-related conditions (e.g., insulin for diabetes) * No requirement for chronic corticosteroids * ECOG performance status 0-2 * Creatinine ≤ 2.0 mg/dL * Bilirubin ≤ 1.5 times normal unless due to Gilbert disease, hemolysis, or disease infiltration of the liver * AST ≤ 2 times normal unless due to hemolysis or disease infiltration of the liver * Negative pregnancy test * Not pregnant or nursing * Fertile patients must use effective contraception * No secondary or other malignancy that will limit survival to \< 2 years * No uncontrolled concurrent illness including, but not limited to, any of the following: * Ongoing or active infection * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness or social situations that would limit compliance with study requirements * No uncompensated HIV without adequate CD4 (\> 200/mm\^3) and requiring HIV medication * No active hepatitis B infection * No known G6PD deficiency * No history of allergic reactions attributed to compounds of similar chemical or biologic composition to alvocidib, cyclophosphamide, rituximab, or other agents used in this study * No prior alvocidib * No prior purine analog therapy * No more than 1 prior treatment with a biologic or alkylating agent * No other concurrent investigational agents